Avidemux does not display the icon and does not have any category, through integration with AppImaged on Linux Mint 19.03 x64 Cinnamon
https://github.com/AppImage/appimaged
Following the guidelines above from AppImaged, I placed Avidemux 2.74 AppImage in the directory:
/home/MY_USER/Applications
See the desktop file that was generated by AppImaged in the folder:
/home/MY_USER/.local/share/applications
See attached image
Please correct these errors
Note: I tested the version in development 2.75 and the same error continues.
Done (https://github.com/mean00/avidemux2/commit/f7ab82120fa1a822ca41b0ecf1a044c2ecdb38d5), thank you for your report.
For a fully featured Avidemux, especially on computers with Intel graphics, please build from source instead of relying on appImage as provided Avidemux appImages don't support hw accel via libva.