1) I need to "hard-reset" the complete state of the talos editor, to restart form scratch.
Some "things" just disappeared, maybe I unintentinally hit a key here and there. For example, the ability to move entities in the world by holding ctrl. is not there any more. However the snap tool by holding alt still works. Also, any method to reset the savegame state fails, so I cant test my puzzle any more. I did all the tutorial (TTP Map Tutorial on serioussam wiki) and everything worked well except the final step, open the sigil-door to finalize the world.