Currently, the file menubar doesn't have any support for checked items, so it is not possible to know whether some item is in selected state or not. Eg: Edit->Track Changes->Record. We need to listen to state change messages sent by loolwsd like we do for our toolbar items (so they are shown in pressed/normal state accordingly).
Pranav Kant committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/online/commit/?id=e032cb72fa230f27a9a90f0b74411b9a3c63c96e tdf#106447: Support checked items in menubar