So I think I got a handle on customization in the editor. For this you will edit flag 1 and flag 2, shown here:
View attachment 89945
Keep in mind that when hovering over an item, flag 2 is listed first, then flag 1, then the item id. Anyways-
Flag 2 edits the first list of customization options cyrus gives you when customizing an item with the default choices. If there is only one aspect you can edit, than this will be the one you edit. To input values, you need to set the dropdown menu to 'custom'. The first option cyrus gives you will be 04, the second will be 08, the third 0C, the fourth 10, the fifth 14, and so on. It's just going up in hex, in increments of 4.
Flag 1 edits the second list cyrus gives you. Same idea on order, except this time it starts at 01 and goes up by 1. So 01, 02, 03, etc. To have the item have the default settings just leave the flag values alone.
All you need is the order in which cyrus offers you...which can be an issue. BUT there are some blogs that do generally list items in the order they are offered, such as
this blog which goes over the RV items. Sadly it is more difficult to find the order for the second round of options, unless it's the stained glass window, which has
guides of the options in order (ignore the modern option, the hex values start at the 'flower' options).
One way to to get around the order requirement is to simply have cyrus customize an item that you know has the same option order as others (if you're doing a set which is probably the most common situation you'll do this) and place it on the map, then copy the values into the flag boxes (remember: flag 2 is listed first when hovering over an item!). I don't know how to make the design be a specific custom design or clothing design, you could try having cyrus make one item with those options and copy what it gives you but I don't know if it'll work. If you just have one item you need to customize and you don't know the order (or one item you do know the order of but no other reason to open the ram editor) it would be quicker to have cyrus customize it and time travel.
I think that's about it.