I'm not familiar with the Reminder function. Does that let you rearrange the order of the split items after it's created? The pay stub from one job is always changing as new types of taxes and benefits are added. I also use splits to manage other things where I often wish I could reorder the items within the split.
But a reminder will remember the order of those splits when it triggers every two weeks for a payroll. Those should be consistent. If you enter the splits and set it up to remind every two weeks, you can see it show up in the reminders and when you click on it the splits will be in the order that you set up the reminder.
If you need to reorder the splits every time you enter that payroll, then that is just not something MD is set up to do.