How do I record my location nightly with Inreach mini?

Tracking  might work, but only because the unit sends an initial track point when you enable tracking and a "finished tracking" message when you stop. However, the unit automatically increases the interval to 4 hours when it senses that you are stationary. If you do try this, be sure that you continue tracking until the first point is sent, then leave the unit on long enough to send the end track point. This has enough imponderables that I would consider something else.

I am not sure that the Mini sends waypoints marked in the field back to the server. All iR units used to do this, as well as sending navigation events. But Garmin has been phasing this out. I don't have an active unit with which to test. If all you want is a record of your location on the Mini itself, this is fine.

If you want a record on the server/MapShare, the absolutely reliable thing is to send a message. Make sure that you wait for a fix (and don't say "send anyway" if the unit offers to send the message without a fix). The message will be visible on the server (and on MapShare if you address it to MapShare, possibly with other recipients). The coordinates will also be available on the Mini when you review the message thread.

There are safety advantages to tracking (via sent point) continuously as you travel. But this will not reliably get you the location of your campsite.