Ok, I did a bit of digging in the parts catalogues and on the internet and I think I figured out G2593.
The kit contains
part of the existing standard control valve (blue arrow) that is replaced and that adds another hydraulic output (red circle) via a diverter valve operated with an additional lever (green arrow).
Here the standard control valve:
View attachment 147266
This is the outer part of the control valve replaced by kit G2593:
View attachment 147267
That's the standard control valve showing where the modifications are:
View attachment 147268
And this is the location on your tractor:
View attachment 147269
The extra small lever is actually just about visible on YOUNGDRETTIs picture:
View attachment 147270
Problem is that G2593 and the valve in the kit are not available any more and since very very few people had implements other than a cutting deck for their G1800 / G1900 this valve seems to be rarer than hens teeth.
But nobody can stop you from attaching a simple three way valve and a lever on the deck lift cylinder output.
Kind regards,
Hugo