One way of doing it would be, to make the length of the list adapt to the messiah interface height. And leave some room for the “more” (I still have it behind my windows task bar).
A scrolling list (like in many other places in messiah) would be a better intermediate solution too.
But the only “real” solution will be, to allow for either user or developer defined sub menus.
Having - for instance - all TLHPro and all AoN: Studio plugins in one submenu each is the way to go. It would also make for an ordered list instead of the current almost-random order.
Everything else is just wasting time (imagine the current solution if you have 250 shaders …)
BTW. You can still select your shaders more conveniently from the “+” signs next to parameter fields in the shader interfaces. This list IS scrolling and works much better for me than the new right mouseclick menus.
Cheers,