Is there any way to put the bar lines in the right place in crooked old time tunes or any tune that changes meter? Or to handle tunes with an extra 8th or 16th note (there are quite a lot of them)?
In almost all cases, the way that a crooked old-time tune breaks out of the normal pattern of 4/4 is with the insertion of a 2/4 “half measure” (or a measure of 6/4, which is the same as 4/4+2/4 or 2/4+4/4).
In Strum Machine, you can select a chord and either use the Chart menu to make a “half measure” or press the “H” key. That will make the selected chart cell into a 2/4 measure.