I just installed a number of extensions (Fredo Tools, Solid Inspector^2, Fredo Corner, Bezier spline, …) on my new install of SU 2019. These did actually install and floating menu bars appeared. I closed the menu bars, closed SU, restarted sketchup and there is no sign of these extensions. No menu items have any of these as a choice, the toolbars are not available under View-Toolbars. There is no plug-ins or extensions menu item in the top menu bar as there was in SU 2014. On the other hand, if I select Window->Extension Manager the plug-ins are all listed as installed. I disabled a number of these and restarted, but they appeared enabled on the restart. I uninstalled a number of these (Solid Inspector^2, Bezier spline) and the problem persists.
I tried starting sketchup using “run as admin” - no difference.
I reinstalled one of the deleted extensions and all the “missing” extensions appeared - both as toolbars and menu items. I left the menus open and closed SU, then re-opened. Everything is gone again.
What do I try next?