I installed the Tutanota appimage and chose to integrate it with the desktop as well. After that, i chose to put the app on the dock as well. Now, whenever i press the tutanota app, a second Tutanota icon appears on the dock, as long as the client is running.
Edit the .desktop file which is "tutanota-desktop.desktop" You can find this file in your home directory under .local/share/applications/ You just need to add the line: StartupWMClass=tutanota-desktop So if your home directory is called b1tanarchy you could do the following: echo 'StartupWMClass=tutanota-desktop' >> /home/b1tanarchy/.local/share/applications/tutanota-desktop.desktop Once you have done that you have just one icon in plank.