As I noticed more and more programs come without an entry for the Debian Menu System, but they do come at least with some .desktop file. Is there a (ready made) way to convert these .desktop files to menu entries one can then place in ~/.menu/?
Got an answer via icewm-user list:
If you are using 1.3.12, try
$ icewm-menu-fdo >~/.icewm/menu
As this would overwrite the custom menu file, it is better to
icewm-menu-fdo > ~/.icewm/menu-fdo and add a new line to ~/.icewm/menu:
menufile .desktop folder menu-fdo which will show the generated entries in a new subfolder '.desktop' in the IceWM menu.
Github has the according bbidulock/icewm repo