Welcome!
One other thing to be aware of is: when choosing a range, say medium, make sure you are fully engaged with the range selector lever, if not, sometimes I've found the selector may disengage and if on a steep hill with a FEL load you may find yourself suddenly picking up speed- so obviously step on the brakes. This is less likely- IMPE with a gear tractor, so just a word of caution. Also, related to HST is the fact that if you let off the forward or reverse pedal the tractor will come to a stop, though it will still roll slowly, depending on slope/load.
Enjoy it!