If it is any use for tracking this bug, I will post some other findings about it.
I duplicated my project scene and deleted all node trees to start from scratch (also removed all Armory Traits from all objects).
Its seems appending an object (with traits) from the bugged project (which was created before installing the logic pack) into the test project brings the bug along.
Only way to add new logic nodes without crashing is to remove the object and its node tree.
While testing with the restarted scene, I was experimenting with combinations of the Lerp Vectors, Vector Mix and Looking At nodes.
When I changed the object to which rotation should be applied, it appears cleaning the project caused Blender to freeze. And the bug was triggered again.
To circumvent the bug, I loaded another project with fewer nodes (only 4 nodes, but one of them is from the logic pack) as suggested and next loaded my test project again.
Back in the test project I could add nodes (standard or pack) without crashing.
On a sidenote: I noticed when I search for Timer Node it shows twice in the list.
Also: the search bar shows 3 “Unknown” nodes and trying to add them results in error.
Thanks for your help.
At least I can sidestep the bug until a solution is found.