This is Drew answer in details.
Configuring emacs menu is tricky but solvable. The problem is that emacs could be built with different visual libraries (like GTK, motif, lucid...) that affect on the menu apperanse different ways not related to emacs.
So what to do:
- Understand which visual library your emacs is build with. Menu Help > About emacs.
In my case I see the line:
GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
that means that my emacs is built with GTK-3 library. Library major version is important because for GTK-2 and GTK-3 configuration are different.
Go to https://www.gnu.org/software/emacs/manual/html_node/emacs/X-Resources.html
and look sublink for the resource of you library (in my case that was "GTK resources")
Find the solution for your case (or google it additionally).
For my case of GTK-3 the following helped:
#pane #menubar GtkMenuShell,
#pane #menubar GtkMenuShell *
to the file ~/.config/gtk-3.0/gtk.css
and menu was bigger after emacs restart.
Useful links for the GTK-3