New Disc Volume Creation Question

Been using my PR2100 for a couple of years now - single 4TB Red disc - JBOD config.
Added an additional 4TB Red disc today & expected something like ‘new disc detected - do you want to configure it now’ - but nothing. Disc shows up ok under ‘Storage/Disc Status’ but not under ‘Storage/RAID’ - only Volume_1 appears.
How do I create a new JBOD volume on my new disc?
Any help much appreciated.

Many Thanks for this reply! I was afraid to try the ‘Change RAID Mode’ option since it was worried my data may disappear from the original disc. Will it? (I’m doing a backup currently to USB in case it does!)

Many Thanks dswv42 for taking the time to advise on this. The solution worked a treat - and as you mentioned the original data on disc 1 was fine.
So, in summary, if you want to add a new disc to a PR2100 (in JBOD config as per the existing disc) do a backup (mine took ages using USB!) then click on ‘Change RAID Mode’ and follow the instructions provided. (Note to WD - this is not initially intuitive & suggest reworking the manual to explain it or the user interface to make it clearer)>