0.4.11-RC-34-g5e059e7 gcc dbg linux.
Photofiltr 7.2.1 from rapps has no taskbar pane currently.
main app displays no pane
main app displays a pane
The application improved a bit recently. In older 0.4.8RC24 it did still have two entries in the taskswitcher https://jira.reactos.org/secure/attachment/45415/Photofiltr.webm
That problem is already fixed.
The application is stronger in taskswitcher than rapps. When I chose to bring rapps to the front, then Photofiltr does steal the activation from rapps. (CORE-16525)