Once you've had a chance to try the feature, fill out the Beta Feedback Form.
It only takes about 10 minutes, but there's no cap on how much you tell us — the more detail you give, the more useful it is. If something comes up for you along the way and you don't want to wait, Lark Meeper can help in the moment, but the form is what actually reaches the team building the feature, so that's where your real feedback should land.