Is this a fresh install or something older that is now experiencing a free space problem ?
If it’s a fresh install then something is wrong with the install and I suggest you redo it
There is a way to allocate more or less to different pools but you need to understand lvm2 a bit.
https://wiki.archlinux.org/title/LVM
Qubes install defaults to luks with ext4 and lvm2 running on that. You have to edit lvm2 with the command line.
I’ve had a few lvm2 systems and only one needed any lvm2 tweaking
Changing the install to btrfs (a different filesystem) is pretty easy. It’s either in advanced options or b-livet