I will attempt to do a clean install of OMV on the SSD
If you are going to do a new installation you have another safer option. Do the Debian 11 installation and during the installation you can create the partitions you need. Then install OMV with the script. You avoid all the gparted hassle.
Even if you want to restore an OMV backup to the installed debian partition you can do that too and it will still work, I have done it before with fsarchiver and it works.