Has anyone here done any save file edits?
I'd really like to edit my custom companions to the same xp as my normal guys, because it's aids that it isn't
I can't say that I know everything that would be involved in editing the xp for your characters, but it was dead easy to edit my gold.
First, find the save file that you want to modify. It is located in C:\Users\SamDaMan\AppData\LocalLow\Owlcat Games\Pathfinder Kingmaker\Saved Games. I install Steam games on my D drive, and the saves were still on C, so I'm assuming they would still be there for everyone else, but obviously check around if it isn't.
The saves will be numbered and literally named whatever you called them in game, like Manual_8_Oleg_s_Trading_Post___16_Gozran__IV__4710___11_52_09.zks if you didn't modify the default name. Easiest way would be to go in game and make a new save so it comes up looking like Manual_8_Edit_XP_Here.zks or whatever. (Manual just means manual save, Auto obviously auto save.)
Make sure you back it up, of course. Assuming you have 7zip or WinRar installed, open the archive with that. Now, the one I needed to edit was player.json, but it is likely that companion xp might be in party.json. Pull a copy of that file out to work on. Open it with something like Notepad++. I suggest a program like that vs. standard Notepad or Wordpad because it deals with keeping formatting and such a whole lot better.
For gold, I had to try various search terms, but eventually I found "money" was what I wanted. It looked like this: "Money":258, (with the comma). I literally just added a 10 to the front so it now said 10258. Notepad++ took care of making sure the formatting was correct (maybe there wasn't any to worry about, but I'd rather not risk it). Then save the file, and then drag it back into the archive you have open. Tell it to overwrite the existing file. Close out the various programs just in case it causes write issues having it open, and load the game up.
Obviously for xp, you're going to have to look for something else. I opened up party.json and searched for "experience" and that seems to be what you want. You'll also find a "GiveExperienceOnDeath" variable but you can skip that one. I didn't see any obvious way to tell which character is in which section, but since it gives a number after "experience" I'm assuming you could just figure out what your main character has in terms of xp, and then change every single occurrence of "experience" to the same number. You might be modifying ones not in your actual party too, but you probably don't care about that much.
Anyway, hope that helps. I haven't specifically done it with xp, but now that you've brought it up I might make everyone match too (once I actually figure out what I want my party to consist of). If it doesn't work, let me know and I'll take a further look at it.