The reason was "Book Covers Skyrim", which is redundant and blows up the leveled lists in case Legacy of the Dragonborn is added to TechAngel85's modlist. :-D Still, I would like to know how I can identify the overloaded lists from wyre bash. TY!
thanks for replying that fast. I've tested a little bit more today and it seems that it all comes down to activated or deactivated "administrator rights". Windows 10 does something diffenrent to Windows 7, where these problems did not occur! I also tried a different storage drive - HDD vs SSD: SSD's only reduce loading times. (sad but true: On my system all MO-Skyrim loading times are longer!)
In the pictures below you can see that I used a fairly "non-modded" skyrim installation. I barely go further than S.T.E.P. core 2D Fixes. FYI: I play in 1440p.
Maddin's post in Wyre Bash: Error message after rebuilding Bashed Patch was marked as the answer