Whenever I try to start some games from the sidebar, their icon just glows a few times and then stops. I've tried if with the following games and they don't seem to work:
I have tried: Licity-NG, Supertuxcart, Stellarium, ect.
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We had a similar issue with our app. Turns out that we use a wrapper to launch it - and it cannot be launched without the wrapper.
However, the icon in the tray is the app's icon, not the launcher's icon.
Removing the & from the launcher solved the problem, since now it's the wrapper's icon that we see.
As to why it cannot be launched without the wrapper? Seems that the app looks for its config files using a relative path - and the icon in the launcher confuses it; it thinks it's located in the launcher.
As to your question: Maybe you can figure out how to add the original icons to the launcher, without launching the apps. (Though you probabaly will then have 2 icons displaying while the app is running.)