Checklist

• I have searched the issue tracker for open issues that relate to the same feature, before opening a new one.
• This issue only relates to a single feature. I will open new issues for any other features.

Is your feature request related to a problem?

See #5633, the mobile simulator on XDG systems does not support theme watching and does not allow sending notifications. This makes the simulator not able to test all features of some apps.

Is it possible to construct a solution with the existing API?

Yes

Describe the solution you'd like to see.

It should be possible to share the desktop XDG handling for these tasks.