For reoccurring shifts, add the option to assign shifts every 1st, 3rd, 5th day of the month, and 2nd , 4th day of the month. There are volunteers who are only able to volunteer the 1st, 3rd, 5th or 2nd, 4th, etc. day of the month.
When you go to Actions > Copy Shift > To a Reoccurring Frequency > Repeat This Shift Every > There should be an option to click every 1st, 2nd, 3rd, 4th, and/or 5th _day of the month.