So, leave it to me to be perhaps the only person in the world that uses this:
In the Multi-Ring Buffer Tool, hitting ALT-TAB does some weird flashing of something, but adds my current distance value to the input then leaves mouse focus on "Distances" so I can keep incrementing without having to move my hands around the keyboard or grab the mouse each time. I was able to do this in about 20 seconds:
In Pro, CTL - TAB, SHIFT-TAB, and ENTER save the current row and start a new one, but no mouse focus in the new row. It takes FOREVER (which is longer than it takes Arc to do the same task) to populate, say, 30 or 50 buffer distances. I have to keep clicking in the next row to begin typing my next integer.