Use a modern interface design
The Disks UI hasn't been updated for a long time, and it shows: it doesn't match other apps which are using modern design conventions, and it doesn't align with the advice in the HIG.
We have an initial set of mockups for a more modern Disks design, and it would be great if they could be implemented. An extract:
The space allocation bar could be left out for now. Maybe that could help with the GTK4 port?