Trigless locks and trigless trigs are variations on the same concept - a trig just does a couple of things a lock doesn’t.
So every lit note on the sequencer is a trig, which can be a bit confusing at first. Regular trigs, as the name suggests, trigger samples. If you’ve made a loop, you already know this. Press a button and it tells the OT to play the sample at that point in the sequence.
But sometimes you want to enter some info to the sequence that doesn’t trigger the sample. Say you have a 1 bar drum loop and you’d like to add reverb to the drums on steps 5 and 13. So you want to add trigs to steps 5 and 13 to alter the reverb send, but a regular trig is going to start your sample playing again, and you don’t want that. This is a job for a trigless lock (or perhaps an LFO, but let’s stay focused).
So instead of pressing the trig buttons on their own, you hold Function and press them. Bam! They turn a dim green. Now hold the trigs down and set the reverb send - job done. That’s a parameter lock, or p-lock. You can also lock other parameters on the same step. When you play the sequence the sample just keeps playing as it passes these parameter locks, hence ‘trigless’.
A trigless trig (possibly the most confusingly named synth feature ever) is the same as a trigless lock except it does two other things: it triggers the LFO and it triggers FX envelopes. So if you want to retrigger an LFO without retriggering the track sample, a trigless trig is your friend. You set a trigless trig by converting an existing trigless lock (hold the trig and press Yes - it turns a brighter green). Most times, a trigless lock is all you want.
Check page 80 of the current manual for more info - that page also covers one-shot trigs. For clearing parameters, see page 87. It generally involves holding one button depending on what you want to clear (e.g. the pattern page button) and pressing Play, which you’ll notice has ‘Clear’ underneath it in red (so it’s easy to remember once you know how).
Hope that helps!