Not sure if I have seen any admin apps or even if they exist but a control panel for either mdadmin, btrfs or lvm raid.
Might be LVM and just a jbod big drive collective.
Raid on linux is extremely easy but to further this and make it easier a web control panel for raid.
Not everybody is comfortable with the command line or RAID for the first time.
Could even be a disk manager where it will help with mounting disks at boot.
BTRFS raid 0,1,10 also doesn’t have the disk limitations of mdadmin and could be said to be even easier as it is able to handle uneven partition sizes and cover what would be odd disk qty’s with standard mdadmin raid.
LVM maybe just a jbod 0/1 RAID.
Anyway think you get the idea 