Allowing arbitrary reordering of zones in a program would require substantial changes to the program data structures as well as the UI design. This is not something that’s easy to do at the moment, not because it’s technically difficult, but because it involves a lot of changes to the program data structure and UI, and making them backward compatible is hard.
But, some limited support for reordering is coming up in the next firmware, as I explained here:
https://github.com/OpenSprinkler/OpenSprinkler-Firmware/issues/232#issuecomment-2256420560
it’s not arbitrary reordering, but it give you a few options to run zones in forward or reverse order of zones indices, forward or reverse order of zone names, alternating (i.e. program’s first run in forward order, second run in reverse order etc.), and completely random ordering.
If you have been looking for an arbitrary reordering of zones feature in a sprinkler controller, that means it’s not a common feature — on traditional sprinkler controllers, you just name a set of zones and the water time of each zone, and it waters them in the order of the station index. I haven’t seen a sprinkler controller that allows arbitrary reordering of zones.
Although the firmware code is written in C++, it mostly uses C only features.
In addition, you can always use a script to send command to OpenSprinkler to run zones in any way you want.