Hi,

Everything that can be done through the “properties” menu can be done through sub-methods,

First, you should ensure the door type used to edit slack for this type of door (here doors Std, edit others types or “Doors” don’t have any effect) 

Now from the doors Sub-method

For single door slack, where applied per edge

Don’t forget to pay attention to the shared edges, like your cabinet Left and centre doors on upright

because by default, the slack is put from the centre of the upright on the left AND the right 

But if you check “Apply a half-slack.”

that divide Slack by 2 here,
2.5mm/2 from open side = 1.25mm
2.5mm/2 from fitting side = 1.25mm

And finally, to have equal doors, you can select all of them and then select the equalize option.
But, this will move uprights, of course.

I personally use 1.5mm everywhere without checking the option, which gives me 3mm of slack between doors and 3mm when reassembling different cabinets, which works in 95% of cases.
I only have to change this manually in case there is a finished side

Hope this helps, 

Cheers, Alex