You can force pair them by dragging one on top of the other. TP will ask you if you want to force pair. I believe they need to be the same category of workout to force pair. And it may be that you have to select the correct category of workout on your Garmin rather than afterward.
Pairing the workouts does not affect your CTL or other metrics although it makes your calendar look nice and tidy.
Mine is a mess because I do the workouts out of order depending on my work schedule, kids, etc.