You probably don't have enough posts to post a link just yet but if you can tell us where, and maybe break up the url
http : // www . somesite . com / blah / peh.html sort of thing that would help.
appears to be a tool that can extract from saves and shove it into a csv (a very simple form of spreadsheet) and then inject it back again.
is what pointed me at it and includes some data.
Anyway not sure what there is to say. https://gbatemp.net/threads/rom-hacking-hex-editors-mid-2012-discussion.326873/
for a list of good hex editors for a kit.
Typically a hex editor has three main sections.
Usually on the left is the address within the file (or memory if memory viewer mode). Probably going to be in hexadecimal. If you are used to page 64, paragraph 3, line 2, word 5 then that is a form of addressing, computers tend to opt for just bytes though. You count along (starting at 0) and go up to... as wide as the thing is by most make it 10h wide such that the numbers on the left go up by 10h each time.
In the middle is the hexadecimal that actually makes up the file. This is values 0 through F, or indeed as most times it is bundled together in pairs then 00 through FF.
On the right is the text decode of the hex section. Usually going to be ASCII ( https://www.ascii-code.com/
) unless you are using a ROM hacking editor which tend to be about doing custom decodes, though some do custom or other less popular things than ASCII for decoding.
You can edit the middle or right section by typing in there.
Depending upon the editor if you press insert (insert, delete, home, end, page up, page down part of the keyboard) then you will probably see OVR flash up in the bottom bar somewhere. This will be overwrite mode, as opposed to insert mode where new data is added and everything else shuffled forward. If you are familiar with the same thing on a word processor then same here, indeed many things will be similar to a word processor -- you can do find and replace, go to location, cut and paste...