Not sure that I´m understanding your question here.

But, you are able to set a trig into a one-shot (see page 79 in manual). As soon as you´ve pressed play AND any one-shot (you can have several in the sequencer grid) has been trigged. It/they will need to be re-armed (by pressing Yes), before being available to any sequencer trig again.

This re-arming can be done at any time, ie before a pattern change are about to happen. And again as soon as any trig (in sequencer) is hit it will play. If you want it to loop you can set the sample itself to loop when its playback has reached the end of the sample. But it won´t be related to the sequencer.

You are able to change between two patterns, where one pattern are using a sample in one-shot fashion and the other pattern using the same sample as a normal sample trig. As soon as you switch between them, the ‘rules’ for the trigs are active. One-shot playing at least once it´s hit (to its full lenght, unrelated to the grid sequencer). And normal sample trigs playing each time an trig is hit, and repeating as soon the sequencer starts over.