Today I added support to mod pre-requisites in the next build (1.38). Here is an excerpt from the updated steam guide:
The game comes with a list of special hidden ‘pre-requisite’ values which may be set to 1 or 0 depending on which country is played, or other factors. You can see the list of these values in this file: data/simulation/prereqs.txt
Here are some of them:
0 = _prereq_has_coast
1 = _prereq_mining_industry
2 = _prereq_deadly_animals
3 = _prereq_preindustrialized
4 = _prereq_royal_family
5 = _prereq_land_border
6 = …
and so on…
These are valuable because you might want to have an event in your mod that is only triggerable if a country has a coastline, and you can add this special value as a pre-requisite to ensure it does not trigger otherwise.
As of build 1.38 of the game, you will be able to add your own pre-requisite values to the game. You simply create a similar named file, in the relevant location in your mod so:
And enter any new pre-requisite names that you would like. Once you have done this, its then safe to make references to the new names elsewhere in your mod, maybe in dilemmas or events.
Note to modders without english as your first language:
‘pre-requisite’ basically means ‘something that needs to be true for this to happen’.