Set Solo Lock Mode ⌥S
The documentation says option-click the Solo button, then select regions, click when done. That doesn’t seem to work for me. If I select regions and option-click the Solo button it appears to work as I expect…
You can mute one or more regions in the Tracks area to exclude them from playback. You can also solo individual regions, to hear them in isolation, and lock the solo status of regions.
⇧ SHIFT – ⌃ CONTROL – ⌥ OPTION – ⌘ COMMAND