'auto arm' sample trigger?

Is there a way to set a sample trig to only trigger the sample if the sample is currently not playing? Something like a ‘legato’ trig?

alternately, is there a way to tell a track with a sample loop to stop at the end of the current loop via a key command?

First question…i do not know right now…I believe there is not such a feature, but workarounds maybe?

For the second question:

You can use Play Free Tracks mode.

If you set a Track this mode, then you can quantize trigger in ONE2 the loop, pressing one time to start and a second time to stop it.
Since it is quantized to PLEN(different options exist too) you can key command it, whenever, to stop as soon as it ends the Master Scale (the Pattern).

In this https://www.youtube.com/watch?v=VMhA8a6SiMU this technique is largely used to achieve Patterns Transitions.