Wow, I stand corrected... I never noticed that there wasn't a solo tool in the piano roll. Sorry about that.
So I was able to do it in 2 steps, that could be assigned to a couple of key commands to work easier:
Select the notes you want to solo.
Next, in the "edit" submenu in the piano, select "Invert Selection"
Next, use the mute tool on one of the notes you don't want to hear and all the selected notes are muted.
Just unmute to hear all notes again.
It's a bit more effort than a solo button, but it works the same.
I've been using Motu DP since 1986, so I'm used to doing things their way. Logic is such a completely different approach it is hard for my old brain to wrap around at times (Though it is my go to program for new projects now). Apologies in advance for dense questions.
Some things are implemented elegantly in Logic and you wonder why DP doesn't make it simpler like that (bouncing) and other things are the opposite (selecting something and hearing it, multiple sequences). So, my impulse is usually, I must not know how to do this, there has got to be a simple way I'm missing.
I've written down a few plus and minus points comparing the two programs, but I don't feel proficient enough in either program to put that out for public consumption.
Sorry to digress.
Clicking on the piano roll keyboard for a particular pitch selects all of those notes. (Drag to select several pitches)
Defaults for L9?
Shift-I set for Invert Selection.
M for Mute (it's a toggle mute/unmute)
Shift-M to Select Muted Events
M to toggle
There is no easy answer to which DAW is the best fit. I've used Cubase and DP at various times. Both have compelling features... However, the overall balance of features/workflow vs head-scratching bewilderment favors Logic in my case.
It's a very personal decision based on efficiency as well as the degree to which the "environment" is conducive to creativity e.g. appearance of the GUI, and number of mouse clicks (in general) to complete high-frequency actions.