Looking for switches

[Avenger]

That switch is like cruise control, but only for engine rpm. Its mostly useful for using the pto. Set your rpm, idle down, then simply hit the switch NEXT to the far right one to rev up the engine again. Kind of redundant when using the hand throttle. But could help.
Think about it this way: You need to start your pto at idle, always. You come into a field or plot to mow, till, whatever. You have your 'cruise control' set to whatever rpm you need (typically the pto speed), turn on the pto at idle, hit the switch (no guessing or adjustments needed), the tractor revs up, drop your implement (or whatever) and away you go. PTO sprayers, at the end of a turn, etc.

I rarely use mine, but its a nice feature that could be beneficial.

 

[smartascii]

I have what appears to be a very similar tractor to yours, an XG3140, and the cruise control/RPM control is finicky to set. It took me several tries to get it to set the first time, but once you get it set, the right-most switch raises and lowers the RPM setting up while the control is activated. It shows the exact target RPM in the gauge cluster. Mine is also a gear tractor, and I use mine to store 540 PTO RPM. Pressing the clutch will drop it back to idle. I find it useful for mowing and running my PTO-driven generator, because the system adjusts the throttle to try to maintain the target RPM when the load varies. There may be other uses I have yet to discover.

 

[karatecop]

On my XG3135, the third from left is to set the pre-selected RPM. The fourth is to increase or decrease the pre-selected RPM once the third button is engaged.