Is it possible to detect 'choices' of previous map in future one without creating FutureMapA, FutureMapB, FutureMapC ?
My friend created very nice campaign but there is problem. Maps are heavy due wavs. Also it looks bad when you install 4 mission pack and get 20 missions .

What we want to do the most is access to bonus mision. Bonus mission will bu unlocked when player completed bonus objective in all 4 missions.
For now what i implemented is this: after each bonus objective player receives message that tells him to remember or write down colour for this mission. After completing mission 4 with bonus objective done bonus map is launched with colored beacons. Player must stand on them in an appropriate order to unlock the mission. This works well but we would prefer to have auto launch of that mission without puzzle or just end of campaing but without additional maps.

Uhm... you're giving the player the bonus map even before he even played any of the maps. He's free to play it whenever he wants. Why bother trying to make it look like you had any control over it? Just add a question to the last map if he completed this map's bonus: "Did you also complete the 3 bonus objectives in the last 3 maps?" If he votes yes (through the voting system of your choice) load the scenario for him.

And also no, there's no way to save stuff from another map, except through modding.

When biophysicist was still around these parts I petitioned him to make a plugin for that but I don't think he got around to it. He said it would work by writing text to a notepad file and then setting switches or death counters based on the text values, essentially coding in features to read text files via triggers. It's way over my head, but farty may be able to help with it when he's not busy breaking patch 1.18.

Death Counters are readable and writable by maps and GPTP and Neivv's teippi plugin, so yeah, the plugin saving a file of a table of death counters at the end of scenario that the plugin later loads into memory at the beginning of another scenario would work.

Make a mod for the campaign and read the .wavs from there instead of from inside each map, you can also hide the bonus mission inside of that. The brood war campaigns uses that method.

I'm looking at doing something similar to this. 1.18 needs to be broken some more before this happens though.