Yes, the current firmware 2.1.7(2) provides a way to switch WiFi network without erasing everything. This is done by pressing B3+B2 (press and hold B3 then press B2, like how you do Ctrl+C). Also, there is a HTTP API that allows the controller to reset to AP mode without performing factory reset:
https://github.com/OpenSprinkler/OpenSprinkler-Firmware/blob/master/server.cpp#L1336
This does require you to have firmware 2.1.7(2) or above though.