I don't exactly have a way to determine what slot is doing what for the plugin, however I tend to just turn on and off the slot pedal and see what it changes, then make notes of that, and for future references. Not all slots will be occupied on each stomp. For most of this stuff, I don't really change much fo the default settings on some of the presets unless I feel it's necessary, but one, that I can assure you is probably a very much mandatory setup is the stop 2 combination of gate/compressor. Slot 1 is the gate, and control 1 of that slot is the actual gate threshhold, which is the most common one I adjust.
As for the tool rack, I don't really care to use it since it's no different than having the instances stored within the preset window where you can assign them, and plus, with the limitation of the rack, I could easily completely open the flood gates of processes within the plugins windows alone, and an a/b switch is easily doable with send processing, that way instead of getting confused, you have a more clear idea of what you're doing.
Here's a setup example that I tend to use for some effects:
Track 1 is the main folder with whatever final stomps and amps in it I desire.
Track 2 is the "A" switch with whatever stomps and amps in it, sending to track 1
Track 3 is the "B" Switch with whatever stomps and amps I want in it sending to track 1, and is also the end of the folder
Track 4 is the input recording track with whatever I desire into it, and sends to tracks 2 and 3.
It seems like much, but this way gives me much more control over what I'm doing and what I want. Also, the whole process tree can be compressed into a folder. IF you want to put track 4 into the folder with 1,2, and 3, be sure it's not sending directly to track 1. You can then control your a/b switching by the levels
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