@MPQ - Thanks, absolutely, but first I complete my editor to be suitable for fast level creation suitable for RTS games, mainly for battles (I started its development because of the special requirements what WED and other game engine level editors do not offer, or what they offer is too complicated for me to understand, because I'm just a hobbyist). Not an easy task, but hard but fun.
These tests are required for the further development as a proof of my ideas. If this basically 2D pathfinding works well, I can improve it to include climbing ladders to walls, using multi-floor buildings and stairs etc. I have the plan and some working codes, and now it seems to be really achievable The pathfinder requires little modifications only. The hard one is the group movement and behaviour. Maybe I should read more about flocking, but there are more simple solutions too (e.g. follow the leader(s)).
Anyway, the pathfinder is suitable not only for groups, one person groups are also okay, a few hundred should be handled without problems even on my old pc... I will test that too.