Off-topic, expand for detailsYes. The file `~/.config/gtk-4.0/gtk.css` is located inside the user's _home directory_. (The `~` symbol means `/home/user` - assuming the user is called `user`, which is usually the case in AppVMs.)
As such, that file is persistent in AppVMs, and that’s where you need to edit it in order to apply the theme in an AppVM.
More information about which directories are persistent in which types of VMs can be found in this section of the documentation:
Another approach is to place the edited file inside the /etc/skel directory of the templateVM, but that’s a little more advanced and I’ll let you search for it. (Searching for /etc/skel in your favorite search engine should give you a variety of Linux articles to choose from. That’s not a topic specific to Qubes OS.)
thanks everyone for bringing customization options to my attention as I have missed that part of docs , adding another auto-hiding panel and launchers does help a lot with convenience , I liked having a context menu (the arrow symbols) for more actions in the same launcher icon
Got the XFCE/dom0 borders working with custom themes.
Added individual windows customization like opacity with devilspie2
Made a custom launcher for easy keyboard shortcuts (Terminal, Files, etc.)
Fixed the XFCE panel, add opacity, round edges, floating with full screen snap working.
Styling of the panel is annoying, I couldn’t change the shadow and margin with css. To get floating snap working, I added a second invisible panel that is sticking to the edge, and full screen windows snap to the invisible panel.
The rounded edges only work on a dark background, if panel shadow is active, else there will be a square shadow at the ends.