Rebuild Grub Menu did indeed get rid of those submenus.
I then proceeded to try making some new BEs, this time using this same graphical Boot Manager tool instead of beadm. These new BEs get added to the grub.cfg as expected.
However, just as with my previous problem with beadm, these do not actually show up in the boot menu displayed when I boot. Only the first two do.
Does no one else have this problem with BEs?
The very first BE I made worked...in fact it's the one I always boot because the default got f-ed up by an attempt to upgrade to 9.2. Note in the screenshot Boot Manager thinks it is the default. However when I actually boot it is NOT the default in the boot menu, "default" is the default and unless I down arrow to the one that works, it boots me into the broken "default".
Also, should the mount point be "-" for these new BEs?
FWIW: this is 9.1-RELEASE-p18