Like you, I used Diskmaster before I used DirOpus, but MenuMaster is
new to me.
MenuMaster was a script configurable drop down menu (or a set of drop
down menus) that allow users to launch any Amiga program from it, as
well as AmigaDOS scripts, CLI/Shell with user defined hot-keys. It was
a precursor of much like Windows desktop toolbar.
The initial version was written in SAS C, then later rewritten in 68K
asm. A companion utility called "MenuEd" was also being developed by
us to provide users a way to add menu items to MenuMaster's
configuration via a drag-n-drop config window by dragging icons to it,
and clicking to select hot keys/qualifier keys. A later version of
MenuMaster was nearly completed that also displayed a menu list
program's '.info' icon file as a small thumbnail beside each entered
program displayed in the user config'd menu.
The program was very configurable/dynamically reconfigurable. My own
MenuMaster config contained something like 20 menus across the
MenuMaster with 10-20 menu items/5-20 sub-menu items.
The program also displayed a small draggable Workbench window (or a
titlebar width window) which itself displayed the system date/time,
and the Amiga's Chip/Fast/Free RAM.
Development got dropped as real world concerns took over for my
partner and I, and development was turned over to someone else.
Haven't used it 20 years, and don't have the original source code any
longer and have no idea if it exists on some Fred Fish disk somewhere
or not. I know the code was placed in the public domain, however.