Now that the Sibelius templates have been updated to correct keyswitching for puffy mallets, how can I go back and fix it in a previous template?

I've already got a score started that I need to do some mallet switches on and I don't want to have to start over in anew score.

It'll work best to copy and paste your old parts into the new template.

To activate keyswitches, select a note where you want the KS change to occur, click a grace note (2nd keypad layout), and enter the keyswitch pitch on the MIDI keyboard. It'll show up as a checkmark gracenote, and you should then hear proper playback.