It’s sounds like you might want to take a look at this video for the Digitakt, I think somebody on the forum created/posted here somewhere too. Basically you P-Lock scenes to a step(s) and sequence the Digitakt externally, then when you press the P-Locked step it activates the P-Locks for as long as the step is held down. I think it emerged as a hack when Trig preview was introduced [STEP + YES]

[EDIT] - He actually made two videos on it:

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