Yes, you can increase the storage capacity by rebalancing the BTRFS filesystem.
First, create a volume with the desired capacity in MacOS.
Next, switch to Asahi and type lsblk to view device information containing the volume.
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
zram0 252:0 0 8G 0 disk [SWAP]
nvme0n1 259:0 0 931.8G 0 disk
├─nvme0n1p1 259:1 0 500M 0 part
├─nvme0n1p2 259:2 0 301.6G 0 part
├─nvme0n1p3 259:3 0 2.3G 0 part
├─nvme0n1p4 259:4 0 500M 0 part /boot/efi
├─nvme0n1p5 259:5 0 1000M 0 part /boot
├─nvme0n1p7 259:7 0 463.2G 0 part
└─nvme0n1p10 259:8 0 5G 0 part
nvme0n2 259:9 0 3M 0 disk
nvme0n3 259:10 0 128M 0 disk
Assuming the device is /dev/nvme0n1p7, add it to btrfs devices.
sudo btrfs device add /dev/nvme0n1p7 /
Afterwards, you balance the endpoint by:
sudo btrfs filesystem balance /
Finally, your storage increased.