OK, so let me get this straight(er) - you have a driver with a maximum output pre-set, and then you can switch between high and low (high being the max output and low being a predefined fraction of that maximum).
Adding a potentiometer allows you to adjust the output of either. So if you're in high mode (say 13A) you can adjust it to 50% (6.5A). I'm assuming this can be done while running giving you a 'dimming' effect? Say your low mode in this example is 5A - if you adjusted your high mode by 50% and then switched to low mode, the low mode would be 2.5A as soon as you switch. The same changes work in reverse as well.
So all if this is controlled by an external switch? I assume it would cycle? So for each press you get on-high-low-off? Then a pot to dim the driver?
Sorry if this is all very basic stuff. I'm one of these 'visual aids' sort of people lol.
Sorry, I guess I lost track of the fact there was an open question on the thread. My apologies for not responding sooner.
Yes, Low is a predetermined (hardware) fraction of High.
Yes, the potentiometer can be changed while running for a dimming effect. If the on-board pot is used, it would be impractical to use as a dimmer in a finished project, but could be used to set the desired output.
If wired correctly, either the on-board or external pot or both can be used to control both modes, as you suggest.
You'd have to have a special switch to get high-low-off with multiple presses. I think there are some around, but they are very uncommon and probably large and expensive. If you really want to use a pushbutton, you'll have to look around and see what's available.
The board was designed with a toggle switch in mind. Think of a standard light switch you might see in your house, but with a center position instead of only up and down. Or the toggle switches used in many canister lights. These are pretty comonly available with three positions, typically called "on-off-on action". Miniature and sub-miniature versions are also available and would be suitable. The way most of these switches are wired, you'd have the center position off, and one side high, the other side low.
This is because of the way the electronics are designed, you have three pins, H, L, C. Connect H to C for high, connect L to C for low, connect nothing to C for off.
For use with an external pot there's a fourth pin, G. Connect the pot endpoints to C and G, then connect the tap of the pot to H or L for high or low mode.