I don't feel like doing that; I have too many "tasks" to complete in my own project. But I can certainly offer some advice.
If I understand correctly, you're willing to do almost everything yourself, and you just need help setting up the creature IDs, right? Well, that's done in the types.xml file.
This file is located in the data archive, and you can open it with Notepad (txt) or, if you want a more comfortable way to work with it, use Notepad++.

That's basically it; at this point, the new creature is linked to its ID number, and the numbering is complete. Then, in the adventure map files, you can write your own names for the creatures that you came up with.

Dear colleagues, thank you very much to everyone who responded. Especially to comrade Waterfall, for the very useful information; I will apply it. And Zobr (sorry if I'm being too formal) also provided a scheme for the MEGA-PACK update earlier.
I would like to convert mods that replace creatures in cities into separate files. For example, Hannik has a lot of interesting creatures in his VK group, but they all (or almost all) replace existing units. My desire and plans are to move the data for these creatures to separate slots. For example, there is a mod that replaces hydras with these creatures.

I want to move it, say, to slot CREATURE_303. Are there any methods for doing this? I know that KOLT, or something like that, released a new mod on NCF that included Hannik's creatures. I want to add more creatures to the MEGA-PACK.