In the German version of Writer in the menu bar the bookmarksmenu is written "bookmarskmenu" (in English and with two exchanged letters).
Could you attach a screenshot by using this link? https://bugs.freedesktop.org/attachment.cgi?bugid=88020&action=enter
I can’t find the typo by using opengrok.libreoffice.org nor by using translations.documentfoundation.org/de. Maybe it is already corrected in a newer version?
Created attachment 111946 [details] menu bar: mistake in writing bookmarksmenu
This menu comes from an extension. You can check what extensions you have by launching menu tools/extension manager. Once you'll find the responsable extension, I'd advise you to check you've got last version of it and if it's the case to contact the author of it.