Download and extract the attached file. You can find 2 folders containing
patron.eaf and
protectorate.esf for ETW and NTW. Suppose that you want to make Britain a patron faction and Portugal it's protectorate:
1. Open startpos.esf, go in [...]\CAMPAIGN_ENV\CAMPAIGN_MODEL\WORLD\FACTION_ARRAY\FACTION\ find Britain and Portugal and write down their Id's (1st line).
2.
In the same instance of EsfEditor open patron.esf and protectorate.esf.
3. Go in FACTION Britain and get further in [...]\FACTION\ DIPLOMACY_MANAGER\DIPLOMACY_RELATIONSHIPS_ARRAY\ and find DIPLOMACY_RELATIONSHIP of Portugal checking the faction Id (step 1) in first line as you can see in the image below.
4. Go in patron.esf, right click on
DIPLOMACY_RELATIONSHIP, copy and then right click in Britain's
DIPLOMACY_RELATIONSHIPS_ARRAY and paste. Now you have 2
DIPLOMACY_RELATIONSHIP the old one (black) and the copied one (green). Right click on the old one and delete. Your changes so far should look the image above.
5. Go in the copied
DIPLOMACY_RELATIONSHIP (green) and enter in first line the Portugal faction Id (step 1).
6. Repeat steps 3-6 but this time in Portugal faction and find Britain's
DIPLOMACY_RELATIONSHIP. Here you'll copy
DIPLOMACY_RELATIONSHIP from
protectorate.esf (step 2).
7. Last thing, go in FACTION Portugal (the protectorate in this case) and enter Britain Id (it's patron) in the line you see red circled in the image below. Save your startpos.esf, you've done it!
The above image is from Napoleon. In Empire the former 2 lines do not exist. Just enter Id under special ability. Few more words about this change. This is the default patron-protectorate relation, where (among other restrictions) protectorate cannot have diplomacy relations with other countries (e.g. cannot declare war). I've discovered that if you do all changes but not step 7 (leave it blank), protectorate is free to apply relations with other factions. This is very useful if you want your protectorate to be playable otherwise it is not.