The Between Z-Levels tool lets you change the Z-level of a path so that it is between two other paths. First select the path to reposition by touching one of its Snapping points. If you have trouble selecting the desired path, you may need to change the snapping Header Option Button from “Snapping to Bottom Path” to “Snapping to Top Path” or vice-versa. The selected path will have a dashed outline. Next, move your finger to one of the two paths that’d you’d like to sandwich this selected path between. It doesn’t matter which you pick first (the top or the bottom) so just for the sake of explanation, let’s say you select the top first. When you’re near a snapping point for the top path, press the Mark Button
The top path will now also be drawn with a dashed outline. Move to the bottom path and again press the mark button. It will be selected and drawn with a dashed outline. Lift your finger now and the path you originally selected will be reposition in the stack so that it’s sandwiched between the top and bottom paths. Here’s an example: