You can and it works for me (with a proviso): rename the plug-in in the middle pane of the plug-in manager and use a custom menu. You have to do *both* for the plug-in to use your name in the FX bin. And, yes, it works for VST3's here (Melda and Cakewalk CA2A are the only ones I've tried with).
Proviso: SONAR is sometimes too smart when you have names starting with the same root and displays the difference in the FX bin (eg. If I have 2 plug-ins named Reverb (Cakewalk) and Reverb (non-Cakewalk), it will display the part in brackets).
Actually, second proviso: some DX effects can't be renamed in plug-in manager unless you run it as admin because of registry key security (Sonitus FX and Cakewalk MFX are like this).