# math extension window on left vanished

Hallo!
I am running Libreoffice 5.xxx and I write math formulas often.
To write math there opens an additional window at the bottom and at the left.
In the left window there are all signs etc. accessible.
**But once it vanished and I am not able to dock it.**
It's only possible to have a separate Window "Elemente" (I assume "Elements")
but I am not able to dock it.
This simple stuff :-( Thank you for help...