Until now, connecting with another Straight Pool Deluxe player meant going through +SPD, and the only way to end a connection was to remove the player from your list. 6.3 puts both on the player row. Tap a Straight Pool Deluxe player in Players and a sheet shows their name and username, whether you are connected, and what you can do about it.
Not connected yet: send a request to connect. If they already sent you one, the sheet offers Accept Request instead, and if they also have games pending against you it asks whether to accept those too. If you already asked them, you can cancel your request.
Connected: Disconnect ends the connection on both sides but keeps the player in both lists, marked not connected, with every game between you intact. From then on a game either of you scores against the other arrives as a request the other can accept, one game at a time, and the app never re-opens a connect request on its own; reconnecting is an explicit request from either side. Remove from Players is still there too and still hides the player from your list only.
Both buttons ask before doing anything.
Step-by-step with screenshots: Connect with an opponent
Thanks for playing — feedback@straightpooldeluxe.com if anything looks off.