There are some apps like Curtail and WebfontKitGenerator, where drag and drop (of images and fonts, respectively) does not work in XFCE. Both these software are available in the AUR. The same issue is present in XFCE with the flatpak versions of these apps.
I have verified that drag and drop works successfully in KDE, Cinnamon and GNOME.
These apps seem to use standard GTK APIs to implement drag and drop.
Is it a XFCE bug? If so, where should I report it (because XFCE has many components) ?
In case it is not a bug, is there any way to fix the issue by slightly modifying the code, or tweaking XFCE settings?
Even in XFCE, I can drag and drop files in Firefox, so it is not that XFCE does not support drag and drop.
Although it is not a Manjaro specific bug (it is XFCE specific, also present in Xubuntu 21.04), I posted it here for some discussion, to know where to report this issue, or how to fix it (then it could be fixed in Manjaro XFCE as well).