Looks like an issue with your installation. Are you using a custom Theme? If so set to a delivered Theme and if that doesn't resolve it, maybe a clean re-install?
I had the same issue and behaviour, but I have forgotten to delete/rename my custom toolbar setting under %appdata%
So SE did a copy of all toolbars from "unigraphics\...." to the new folder Siemens\...
So I stopped SE, renamed that folder and started again, where all toolbars/menu where visible again
Yes this exactly is the correct folder!
I assumed that everybody knows the Windows variable "%appdata%", which brings You to that folder when be entered in the command line of the explorer.
Sorry for that!
And this is/was the place where SE saved the user custom settings for his user interface.
And when this folder of an old version is in place, SE copies it when starting a new version the first time.
But then - and this was the case very often - people were missing new features and function in their multi tab menu, or I suppose, had this strange behaviour, we have seen when starting 2019 the first time.