Hi! Support here to weigh in. It’s pretty much just as I described in the recent thread:
Anyway, what you’ll need to do is create a new goal with the integration settings you want (the graph doesn’t matter and will be deleted), and then send an email to firstname.lastname@example.org to ask us to switch it over. You’ll need to include the link to the old goal and the new goal – naming it something like “temp-run” will make it easy for us to tell which one is which. We’ll switch the new autodata info into the goal, and then delete the temporary one.
In some cases there might be an issue with the new data source overwriting recent data from the other data source. In those cases, we’ll need to fix up the graph for you… but it usually isn’t a problem, and we can easily do that.
If you wanted to be absolutely iron-clad sure there was no gap in your data, you’d want to record everything in both services (Fitbit and Garmin, in your case) for a week so if any data gets overwritten, it just gets overwritten with the same info… but I honestly wouldn’t recommend it and I don’t think I’ve seen any problems with this kind of thing lately!