Yes there is since LXD 5.8:
But there was a problem with it when combined with using -s flag for specifying the storage pool which was fixed in LXD 5.9. These changes should be in the forthcoming LXD 5.0.2 LTS release too.
E.g.
lxc launch images:ubuntu/jammy v1 -d root,size=15GiB
Is equivalent to:
lxc init images:ubuntu/jammy v1
lxc config device override v1 root size=15GiB
lxc start v1
It can be used to override any device setting, not just disk size.
If you use an image with cloud-init in it the guest will notice the larger disk size on boot and grow the guest filesystem too. Otherwise that needs to be done manually inside the VM, as LXD does not know/dictate what partition layout or filesystem a VM uses.