Since I found with searchable app menus / start menus that I don't ever navigate through menus but just start typing, I ditched the menu entirely and have KRunner bound to the Win key. Not only is it fine with any desktop app GTK or not (that packagers have ensured will install with its FreeDesktop metadata file or some such), it supports all the enabled KDE Search plugins. So I don't ever open a calc app again, either..

Sorry but no, the parent commenters looked for a global menu within an application (File -> Open, File -> Save, etc.)

by the way, on macOS the global menu is searchable, too. Shortcut is Command+Shift+/