I know its been half a year since you asked but MAYBE someone else looking for answer to the same question will read this and get answers they need.

Favourites are saved as an .xml files in

C:\Users\"whatever your user name is"\AppData\LocalLow\Ludeon Studios\RimWorld by Ludeon Studios\WorkTab_Favourites

if you dont have "show hidden folders" checked in windows just go to address bar and type %appdata%, it will take you to AppData/Roaming so go up a folder to see LocalLow.

Also, this can be used to "save" favourites in case something breaks them, make your self a folder "backup" in "WorkTab_Favourites" folder and copy your favs there. There are mods, like Simple Slavery, that make mess of things. You set up detailed custom priorities for sub jobs for a slave, than slave has escape attempt, he is temp removed from colonist list and so the work tab, than after his "time out" joins back, his main jobs retain priorities but all sub jobs get reset to the level of main job they are under. Game treats it as if you did those changes and favourite you had gets overwritten. In that case simply delete the favourite, go to your backup folder and copy backup xml of that favourite, put it in WorkTab_Favourites, go back in game, click load favourite, tadaaaaaa.

haha thanks I mean I already found out but your right, good Idea to keep that archived. I helped somone 2 years after commenting somewhere on a problem with ONI cause he read my answer from 2 years back

About the favorites, it would be much helpful if there's an easy way of reverting all assigned favorites to default.

I believe priorities in custom favorites still are not correctly saved when you save the game with a pawn having incapability. This makes me to unload all the favorites assigned every time i need to manually save the game. I remember Fluffy saying 'its on the list' long ago.

So... i hope a button that unloads all the custom favorites added.

oh so that was problay the bug I saw. Thanks for pointing out. I guess I will backup my about 50 Fav. long list of jobs (using job menu so its even more pain in the butt to reasign everything), but I guess a fix to that would be (if you dont have THAT MANY) to copy all favourites and if one goes loss, you can simply load the copy and delete the original.
But thanks for pointing out, had a pawn die of drug overdose (drug-friendly trait causes Pawns to take drugs around 3 times a fk day (as soon as theire "drug need" falls unter 97%, comleptly ridicoulious) and his favourites were resettet, forcing me to do the ♥♥♥♥ new

well there is a easy way isnt it. You simply go in your job board, look for the incapable pawn (since he is the only one being resettet) and unload priority. If you saved it under a name, you can rechoose it right after. But its stil micromanegement times 10 to remember that