Hi Bass,
What I’ve done with a song that I know I’m going to play at an event is put the last 8 measures of the song in a Composer file. It will hold up to 16 measures. I find it easier to build the end of the song in the sequencer and just put the sequence in the Composer. This will allow you to play all but the end of the song live then just play along with the Composer in your right hand and turn the tempo down with your left hand for the ending. Of course this is only good for a specific song. It’s likely someone will have a better idea for you.
Frank