Where should I start with modding?

It immediately reminds me of a joke: I was following your recipe to cook chicken, but instead of chicken, I used fish, instead of pepper, I used paprika, instead of onion, I used bananas, etc. The result was an inedible mess, so I gave the author a thumbs down.

95% of the editor's tables are available for modification; I didn't understand what you were referring to.

Apparently, I misunderstood the point about the data. The joke is certainly relevant, and I didn't mean to offend you. Regarding the inaccessibility of data, I couldn't find where the scripts for perks like "Uncover Secret" and "Scholar" are modified. I also didn't see if there's any probability distribution for perks or if they always drop randomly. I didn't find where the file for the "Vigil" skill (of the Knight) is located. Also, I couldn't find where the data for modifying core skills like attack, defense, logistics, and magic resistance is stored. I did find information about combat machines, but I don't remember if all the parameters are configurable there.
There's a lot of information about all of this, including tables with names and lists, but many of them are not modifiable and are simply provided for informational purposes rather than for modding.

For example, there are two skills in the game: "Scholar" and "Battle Frenzy." Which skill would 90% of players choose? I think it's obvious that in 90% of cases, "Battle Frenzy" would be the more profitable choice. Therefore, I would like to revitalize the underused skills so that there is more room for building different character builds in the game. For single-player, useless skills are fine, but for Multiplayer, the usability and usefulness of skills are much more important.

I would also like to delve into editing the parameters of the "Ritual Pit" (the building where you can sacrifice units and, in return, receive an increase in Minotaurs and Furies). In Multiplayer, I have never used this building, although it could be balanced and made more useful. I found a file with the building's description, but there were no modifiable parameters in it, which means all the information is stored elsewhere.