I probably have made a mistake with the process and I am now stuck. In summary:
installed debian 12 and manually partitioned the install disk to create a 64GB omv-os partition leaving the remaining space on the disk free (approx 400 GB)
installed omv using the install script and checked all is working fine
used fdisk to create a new linux partition with the free space from the cli
rebooted omv and using fdisk the partitions on the disk look fine so the partition has been created and partition table updated - see below
So at this point I thought I would be able to create a new file system in omv gui but there is nothing available in the drop down in create file system...
I am thinking that I should have created the additional partition while installing debian...
Is there anything I can do - such as create the file system using cli and then just mount it using omv?
Command (m for help): p
Disk /dev/sda: 465.76 GiB, 500107862016 bytes, 976773168 sectors
Disk model: Samsung SSD 850
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 93EF5F05-B80C-4281-9094-24F970F92930
Device Start End Sectors Size Type
/dev/sda1 2048 999423 997376 487M EFI System
/dev/sda2 999424 125999103 124999680 59.6G Linux filesystem
/dev/sda3 125999104 976773119 850774016 405.7G Linux filesystem
Command (m for help):