Welcome to the Dorico forum.
I’m not sure of the exact syntax, but if you put a letter r or l in front of the fingering (for example r1,2 in the popover) it will affect the order of the finger numbering. Making a change might depend on whether it is already left or right, so you will probably need to experiment a bit. If you need to flip the position of the fingering from above to below the staff, or vice versa, do that in Engrave mode because in Write mode selecting the fingering selects the notes as well (fingering is treated as a property of a note).