Is it possible to back up the presets of my RH750 head onto a computer or any other device? I play two completely different styles that use all 3 presets for each so i have to sit down before each show and reprogram the presets for that style.
The 3-preset on the RH heads are essentially there to allow different settings, each suitable for different basses. For instance if you play two basses, one fretted bass and one fret-less bass, the 3-preset option will help you to adapt to the different sound of each bass.
There is no option to make a back up of the presets on the RH heads. it is only possible to reset your amp to the factory settings, which will result in all settings of the 3-presets being reset to noon.
Here is how to reset your amp to factory settings.
That being said, a suggestion could be to take photos of your different settings on each preset. Do not forget the settings which are reachable with the SHIFT button. This would mean 2 photos per preset: The first of your settings without having pressed SHIFT. And the second, when you have pressed SHIFT in order to access the center frequency of the EQ bands.
You should get something like this: