Hi
That’s not how UEFI works… if both use the same directory name (user nrickert changes the folder name), so easier to create another esp on the second drive…
Else you using the existing install rename the opensuse folder to say leap423 and then update the efi location from opensuse via;
efibootmgr -c -L "openSUSE Leap 42.3" -l "\\EFI\\leap423\\grubx64.efi"
You would need to delete old entries via efibootmgr -b N -B N (where N is the ref number), also probably set the default boot order as well… then you are stuck with manual maintenance…
os-prober will find across any disks installed…
Running grub may/will overwrite the existing info…
I had a quad boot setup running and two esp’s sda booted windows and Leap, other disk booted Tumbleweed and SLED (SLE uses a sled and sles for directory names) but Leap and Tumbleweed use opensuse…hence the two esp’s 