Workstation 15.5.6- RHEL 8.2 Linux Guest and Secure Boot

I recently created a Red Hat Enterprise Linux 8.2 Guest installation as 'UEFI'. This seems to run o.k. (running on a Windows 10 1909 Host).

I was thinking I could now enable 'Secure Boot' for this in the advanced settings, but I see that the option is grayed out.

Is there a trick to enabling this? Or is this not supported?

It looks like I can enable secure boot for Windows 10 Guests (well, the box is check-able at least)..

Thanks;