Add an appimage application to the top menu bar

AppImages have limited integration with your desktop environment. You can manually add a launcher to your menu, but there is also a tool in development that can integrate appimages

Manual approach

You can manually add a launcher for your AppImage in the dash. Once it is there, you optionally will be able to pin it to the Dash/Dock.

Commonly, the AppImage provides an icon and a .desktop launcher file that you can use for a start. Retrieve it from within the AppImage file as follows:

1. Make sure the AppImage is running.
2. Using the command mount in a terminal, find out where the AppImage is mounted in your file system.

For example, in my little test, I see an entry for an AppImage appearing as

LibreSprite-8ac9ab1-x86_64.AppImage on /tmp/.mount_LibreSyxGgsk type fuse.LibreSprite-8ac9ab1-x86_64.AppImage (ro,nosuid,nodev,relatime,user_id=1000,group_id=1000)

in the terminal output of mount. It reveals that the AppImage is mounted under /tmp/.mount_LibreSyxGgs.

3. Navigate to the folder where the AppImage is mounted using your file manager. In most cases, you will find icons there and a .desktop launcher, in the main folder or in a subfolder.
4. Copy the icon file to the folder .local/share/icons in your home folder.
5. Copy the .desktop file to the folder .local/share/applications in your home folder.
6. Open the copy of the .desktop file you created, and edit the Exec= line (and also the TryExec=line if present) to include the full pathname of your AppImage. Check on the Icon= line if it corresponds with the basename of the icon file you copied (just the basename, no need for the extension). If needed, update. You can also provide a full path to the specific icon file.

This will cause the .desktop file to be picked up in your application menu, i.e., the Application Overview in standard Ubuntu with Gnome Shell.

Automating using the tool AppImageLauncher

If you work frequently with AppImages, then you could explore the tool "AppImageLauncher". That tool is a regular application, designed to associate with .AppImage files. When you click an AppImage file, the tool will automatically copy it to a standard folder (by default ~/Applications) and create a desktop launcher for it.