- Assuming the pedals are connected to the Garmin via ANT+ (which I believe is the default?) you can leave them as an active device without a need to remove them.
The steps above seem largely focused on the BLE side of things and making sure you don’t have any other app trying to access the BLE channel of the pedals and trainer. And unless you are actually trying to use your Garmin inside while using the TR app, I don’t see a reason to worry about that connection path.
As a side, much of this seems focused on the desire to calibrate the trainer (and pedals?) within the TR app. For reference, that is not strictly necessary. I actually prefer to use the Wahoo app to calibrate my Kickr, and typically use the appropriate app that matches any power meter I own for calibration.
This works because once calibrated in any app, the trainer and pedals store that calibration setting and apply it to ANY other app or connected device. So, you can use the Wahoo app to set the trainer calibration, then just use that in TR with no need to use TR for calibration.
There is some convenience to using TR as the calibration app for sure. But keep in mind that the Core, Kickr and other wheel off trainers really only need to be calibrated when moved to a new location and then again about every 2-4 weeks. I do a calibration on my Kickr in the Wahoo app at the start of each month and never touch it in TR. It’s setup in the same room all the time, so there is no need to calibrate more frequently.
Not sure on your trainer room and setup, but that more rare calibration process is a way to simplify your use and maybe get around any conflict you may be having with calibration.