There are a few keyboard shortcuts listed in the 2022 manual that are related to Thru:

Alt+F11: Select Thru harmony.
Ctrl+F11: Select favorite Thru harmony.
Shift+F11: Allow Thru Harmony.

This is found in Chapter 15 of the manual, under the "Editing Song" heading: https://www.pgmusic.com/manuals/bbw2022full/chapter15.htm#keystroke-commands-hot-keys


Best,
Chantelle