A tool for editing an application menu in Lubuntu is called ‘menulibre‘, it is available in standard repositories.
I had to edit ‘Menu -> Internet -> Linphone’ – after downloading and updated snap package of Linphone the menu entry became broken and could not launch the application, so I needed to edit the path to the new update package.
If to edit it manually (without MenuLibre), it is located here:
~/.local/share/applications/linphone.desktop