Map-area discovering (saving the state) seems to be bound to the SetPersistenVariable function/Message. From what i could find it may correspond to
an entry in an .ini file. The message i think takes arguments like: category, variable, value which i think are sections like:

[MapCompletion]
Hawksmouth = 412123

(I made that up, but it could be similar)

As there's the category, i would believe there are other cases where knowledge about it could be relevant.
I coudn't find out how and what, but maybe someone of you can?

Map-area discovering (saving the state) seems to be bound to the SetPersistenVariable function/Message. From what i could find it may correspond to
an entry in an .ini file. The message i think takes arguments like: category, variable, value which i think are sections like:

[MapCompletion]
Hawksmouth = 412123

(I made that up, but it could be similar)

As there's the category, i would believe there are other cases where knowledge about it could be relevant.
I coudn't find out how and what, but maybe someone of you can?

Those are being saved in the database on the server. SetPersistentVariable takes 3 arguments: Context ID, Variable ID and Value.

For the map exploration it's context id 100, variable id corresponds to the map section id's and the value is '1' for explored, '0' for undiscovered.

Search for the GED files and look at the SectionIDs in there. They'll tell you the possible values for the variable ids. Example: Quarterstone has 'SetProperty,SectionIDs,"200,201,202,203"'

Nice, thanks, that works!
And another part of the world login packet deciphered :-)