Ender 3, Ender Extender, SKR Pro-V1.1, with SKR UPS

I have an Ender 3 (standard) with the Ender Extender 400X400X500 kit upgrade. I have the SKR Pro-V1.1 board (I want to use 3 extruders), and I have the SKR UPS I would like to use. This board is not on your list of the “firmware builder” site. I need this firmware any assistance would be appreciated, thanks in advance

I can’t support this board at the moment - as the code to reassign additional steppers beyond X / Y / Z / E is missing.