Hide desktop entries
Apps in the menu are defined as .desktop files here:
/usr/share/applications/usr/local/share/applications~/.local/share/applications
To hide an entry called app.desktop, create this file in ~/.local/share/applications:
app.desktop
[Desktop Entry]
NoDisplay=true
If the entry is already in ~/.local/share/applications, append NoDisplay=true to it directly. It might get overridden.