@Dave-R thanks for your reply. I installed/repaired SketchUp, running by Administrator.
I use SketchUp since 2006 (and give courses since 2012) and always I could drag out some tools from the Large Toolset and place them in another toolbar. I noticed that I can make a whole new toolbar and drag the few tools from the Large Tool Set in there. If it is not possible anymore to customize the toolbars by dragging in tools from another toolbar then will be the solution to make a whole new toolbar.