IMPORTANT: as you read what I wrote, keep in mind that I am no longer maintaining StationPlaylist add-on (for now).
What is the version of Studio you are using? If you are using Studio 6, please DO NOT use add-on 21.11 - please use add-on 22.01 which provides improved (albeit limited) support for Studio 6. At the moment StationPlaylist add-on 22.01 is not available from community add-ons website, but I can assure you that this release was queued for distribution on community add-ons website not long ago. If you are using Studio 5.x, I may need to look into it if and only if the NVDA community does not find someone who will maintain StationPlaylist add-on in several months (I say this so whoever decides to maintain the add-on can step up and resolve this for you before I revisit this issue).
Regarding announcing remaining time for carts, it won't be possible to assign Control+Alt+T command since carts can be played on top of the track you are playing (if I remember correctly). It is indeed possible to obtain the remaining time for the playing cart and add a command to announce this. My hope is that whoever decides to maintain StationPlaylist add-on would implement this feature request, and as I said above, if no-one volunteers to step up in several months, I will do it but as a last resort.
As for NVDA not announcing the name of the assigned cart in Cart Explorer, I need a debug log from you (write to me privately please) no later than January 10, 2022 so I can determine what's going on.