You can assign multiple Serato DJ Pro functions to a single MIDI control (button, knob, fader).

Enter MIDI mode and click on a function you wish to map as in this section of the manual. 

If a MIDI control has already been mapped to another Serato DJ Pro function you will be presented with the option to Overwrite the mapping or Add an Additional mapping.

Pressing ‘O’ will Overwrite ALL of the previously assigned mappings. Pressing ‘A’ will Add an Additional mapping to the already assigned MIDI control.