Since it's unlikely the editor will be used, here's all you need to know to modify the inventory manually.
Device ID offset: 205,892
Slot size: 68,624
Inventory offset: 2,788
The file you're looking for is called honeySave.bin. You'll need a HEX editor, there are several free ones out there.
The save file is organised into 4 blocks. The first three are save slots, 68,624 bytes worth of data each. So if you want to modify the bag contents in the quicksave slot (Slot 3) for example, you'll need to go to offset (68,624 * 2) + 2,788 = 140,036. Once there, you'll have a list of item ID and item quantity pairs. Each value is 16-bits (2 bytes) in size. So a single slot in the bag takes up 4 bytes, the first two for the item ID, and the second two for the item quantity. There are enough slots to fit every item.
The Device ID is 4 bytes long. You'll need to change it if you're moving save files from one 3DS to another, or to the PC.
The save has no error checking believe it or not - so no need to worry about checksums or anything.
Here is a list of all the items IDs:
1: Cypress Stick
2: Soldier's Sword
3: Copper Sword
4: Steel Broadsword
5: Platinum Sword
6: Dream Blade
7: Falcon Blade
8: Über Falcon Blade
9: Zombiesbane
10: Zombie Slayer
11: Dragonsbane
12: Dragon Slayer
13: Blizzard Blade
14: Miracle Sword
15: Über Miracle Sword
16: Bastard Sword
17: Liquid Metal Sword
18: Double-edged Sword
19: Über Double-edge
20: Rusty Old Sword
21: Dragovian Sword
22: Dragovian King Sword
23: Rapier
24: Templar's Sword
25: Hell Sabre
26: Holy Silver Rapier
27: Fallen Angel Rapier
28: Shamshir of Light
29: Mercury's Rapier
30: Bronze Knife
31: Dagger
32: Poison Moth Knife
33: Assassin's Dagger
34: Icicle Dirk
35: Poison Needle
36: Falcon Knife
37: Imp Knife
38: Sword Breaker
39: Eagle Dagger
40: Iron Lance
41: Holy Lance
42: Long Spear
43: Partisan
44: Battle Fork
45: Sandstorm Spear
46: Demon Spear
47: Hero Spear
48: Metal King Spear
49: Boomerang
50: Reinforced Boomerang
51: Edged Boomerang
52: Metal Wing Boomerang
53: Razor Wing Boomerang
54: Swallowtail
55: Flametang Boomerang
56: Stone Axe
57: Iron Axe
58: King Axe
59: Moon Axe
60: Bandit Axe
61: Golden Axe
62: Battle-axe
63: Conqueror's Axe
64: Oaken Club
65: Giant Mallet
66: Sledgehammer
67: War Hammer
68: Über War Hammer
69: Megaton Hammer
70: Flail of Fury
71: Flail of Destruction
72: Thorn Whip
73: Leather Whip
74: Snakeskin Whip
75: Chain Whip
76: Dragontail Whip
77: Spiked Steel Whip
78: Demon Whip
79: Scourge Whip
80: Gringham Whip
81: Farmer's Scythe
82: Heavy Hatchet
83: Bardiche of Binding
84: Hell Scythe
85: Steel Scythe
86: Wizard's Staff
87: Lightning Staff
88: Staff of Divine Wrath
89: Magma Staff
90: Staff of Antimagic
91: Rune Staff
92: Staff of Resurrection
93: Magical Mace
94: Hunter's Bow
95: Great Bow
96: Short Bow
97: Odin's Bow
98: Cheiron's Bow
99: Eros' Bow
100: Plain Clothes
101: Bandit's Grass Skirt
102: Wayfarer's Clothes
103: Boxer Shorts
104: Dancer's Costume
105: Leather Kilt
106: Leather Dress
107: Templar's Uniform
108: Fur Poncho
109: Cloak of Evasion
110: Bunny Suit
111: Silk Bustier
112: Magic Bikini
113: Spangled Dress
114: Posh Waistcoat
115: Magical Skirt
116: Shimmering Dress
117: Dark Robe
118: Dangerous Bustier
119: Divine Bustier
120: Jessica's Outfit
121: Leather Armour
122: Scale Armour
123: Chain Mail
124: Bronze Armour
125: Iron Cuirass
126: Iron Armour
127: Tortoise Shell
128: Full Plate Armour
129: Silver Cuirass
130: Dancer's Mail
131: Silver Mail
132: Dragon Mail
133: Magic Armour
134: Zombie Mail
135: Heavy Armour
136: Spiked Armour
137: Platinum Mail
138: Bandit Mail
139: Sacred Armour
140: Gigant Armour
141: Mirror Armour
142: Liquid Metal Armour
143: Dragovian Armour
144: Metal King Armour
145: Silk Robe
146: Leather Cape
147: Robe of Serenity
148: Magic Vestment
149: Flowing Dress
150: Sage's Robe
151: Angel's Robe
152: Velvet Cape
153: Crimson Robe
154: Princess's Robe
155: Dragon Robe
156: Pot Lid
157: Leather Shield
158: Scale Shield
159: Silver Platter
160: Kitty Shield
161: Bronze Shield
162: Templar's Shield
163: Iron Shield
164: Light Shield
165: White Shield
166: Steel Shield
167: Magic Shield
168: Dragon Shield
169: Power Shield
170: Saintess Shield
171: Bone Shield
172: Mirror Shield
173: Ogre Shield
174: Silver Shield
175: Big Boss Shield
176: Ruinous Shield
177: Thanatos' Shield
178: Goddess Shield
179: Dragovian Shield
180: Metal King Shield
181: Bandana
182: Leather Hat
183: Hairband
184: Pointy Hat
185: Feathered Cap
186: Turban
187: Silver Tiara
188: Bunny Ears
189: Stone Hardhat
190: Iron Helmet
191: Fur Hood
192: Bronze Helmet
193: Coral Hairpin
194: Pirate's Hat
195: Iron Mask
196: Hermes' Hat
197: Platinum Headgear
198: Magical Hat
199: Happy Hat
200: Hades' Helm
201: Slime Crown
202: Mythril Helm
203: Mercury's Bandana
204: Scholar's Cap
205: Thinking Cap
206: Iron Headgear
207: Raging Bull Helm
208: Golden Tiara
209: Great Helm
210: Phantom Mask
211: Skull Helm
212: Dragovian Helm
213: Sun Crown
214: Metal King Helm
215: Agility Ring
216: Meteorite Bracer
217: Strength Ring
218: Gold Ring
219: Prayer Ring
220: Recovery Ring
221: Goddess Ring
222: Gospel Ring
223: Life Bracer
224: Mighty Armlet
225: Gold Bracer
226: Ruby of Protection
227: Titan Belt
228: Scholar's Specs
229: Tough Guy Tattoo
230: Slime Earrings
231: Devil's Tail
232: Fishnet Stockings
233: Garter
234: Lady's Ring
235: Gold Rosary
236: Sorcerer's Ring
237: Skull Ring
238: Holy Talisman
239: Ring of Awakening
240: Full Moon Ring
241: Ring of Clarity
242: Ring of Truth
243: Ring of Immunity
244: Catholicon Ring
245: Dragon Scale
246: Elevating Shoes
247: Medicinal Herb
248: Antidotal Herb
249: Moonwort Bulb
250: Strong Medicine
251: Special Medicine
252: Lesser Panacea
253: Greater Panacea
254: Rose-root
255: Rose-wort
256: Strong Antidote
257: Special Antidote
258: Moon's Mercy
259: Mystifying Mixture
260: Yggdrasil Leaf
261: Yggdrasil Dew
262: Amor Seco Essence
263: Chimaera Wing
264: Holy Water
265: Magic Water
266: Elfin Elixir
267: Rockbomb Shard
268: Sage's Stone
269: Seed of Strength
270: Seed of Agility
271: Seed of Defence
272: Seed of Wisdom
273: Seed of Skill
274: Seed of Life
275: Seed of Magic
276: Mini Medal
277: Thief's Key
278: Magic Key
279: Ultimate Key
280: Orichalcum
281: Bunny Tail
282: Timbrel of Tension
283: Baumren's Bell
284: Gold Nugget
285: Iron Nail
286: Cowpat
287: Dragon Dung
288: Rock Salt
289: Saint's Ashes
290: Wing of Bat
291: Magic Beast Hide
292: Fresh Milk
293: Rennet Powder
294: Red Mould
295: Waterweed Mould
296: Premium Mould
297: Plain Cheese
298: Spicy Cheese
299: Super Spicy Cheese
300: Scorching Cheese
301: Cool Cheese
302: Chilly Cheese
303: Cold Cheese
304: C-C-Cold Cheese
305: Double Bubble
306: Eau de Monster
307: Super Seed of Skill
308: Mild Cheese
309: Cured Cheese
310: Angel Cheese
311: Hard Cheese
312: Soft Cheese
313: Chunky Cheese
314: Highly-Strung Cheese
315: Crystal Ball
316: Tool Bag
317: Jessica's Letter
318: Templar's Ring
319: World Map
320: Venus' Tear
321: Moonshadow Harp
322: Sand of Serenity
323: Lizard Humour
324: Argon Heart
325: Great Big Argon Heart
326: Magic Mirror
327: Sun Mirror
328: Stone Sword
329: Kran Spinels
330: 'The Big Book of Barriers'
331: Marta's Bag
332: Illuminated Sea Chart
333: Nook Grass
334: Godbird's Soulstone
335: Darktree Leaf
336: Templar Captain's Ring
337: Argon Ring
338: Echo Flute
339: Eros' Bow Recipe
340: Imp Knife Recipe
341: Dragon Slayer Recipe
342: Thief's Key Recipe
343: Morrie's Memo #1
344: Morrie's Memo #2
345: Morrie's Memo #3
346: Monster Arena Key
347: Godbird Sceptre
348: Gold Orb
349: Silver Orb
350: Red Orb
351: Blue Orb
352: Green Orb
353: Yellow Orb
354: Purple Orb
355: Copper Monster Coin
356: Silver Monster Coin
357: Gold Monster Coin
358: Flame Shield
359: Ice Shield
360: Erdrick's Sword
361: Demonsbane
362: Dread Dagger
363: Golden Gar
364: Black Buzzard
365: Bad Axe
366: Candy Cane
367: Honking Hammer
368: Wizardly Whip
369: Slime Stick
370: Night Sniper
371: Iron Claw
372: Fire Claw
373: Cobra Claw
374: King Cobra Claw
375: Beast Claw
376: Beast Talon
377: Dragon Claw
378: Dragonlord Claw
379: Orichalcum Claw
380: Gryphon Talon
381: Iron Fan
382: Peacock Fan
383: Rainbow Fan
384: Stellar Fan
385: Lunar Fan
386: Solar Fan
387: Dryspell Fan
388: Kaleidoscope
389: Fan of Peace
390: Big Bad Boss Shield
391: Gothic Mitre
392: Dogsbody's Hood
393: Hexlet's Hat
394: Kunoichi Headband
395: Mad Cap
396: Gothic Vestment
397: Dogsbody's Vest
398: Nitid Tutu
399: Hexlet's Skirt
400: Abiding Blazer
401: Oriental Warrior Wear
402: Butler's Best
403: Jester's Outfit
404: Cap'n's Clothes
405: Mandarin Dress
406: Kunoichi Costume
407: Über Sacred Armour
408: White Gold Bell
409: Darksteel Bell
410: Ethereal Stone
411: Alistair's Armour
412: Metal Slime Earrings
413: Fire Dragon Charm
414: Light Dragon Charm
415: Lord's Bracer
416: Super Double Bubble
417: Super Seed of Agility
418: Super Seed of Defence
419: Super Seed of Strength
420: Super Seed of Wisdom
421: Super Seed of Magic
422: Super Seed of Life
423: Metal Slime Platter
424: Healie Hat
425: Healie T-shirt
426: Hearty Ring
427: Lucky Pendant
428: Golden Slippers
429: Ye Olde Sword of Erdrick
430: DUMMY 7
431: DUMMY 8
432: DUMMY 9