I have an 830 running f/w 3.20.
I have a few ConnectIQ data fields loaded - flyingflo's Heart Rate Graph (https://apps.garmin.com/en-US/apps/ee19c377-c1a8-4595-87f1-039c28b1ac00) and a couple I have written myself.
These all work fine in the default Road profile, but I cannot add them to any other profiles - they appear in the field browser, but when they are selected, the Timer field is shown instead.
The only way I have found to have these data fields in more than one profile is to set them up in the Road profile, duplicate that profile and then change it - so my Mountain Bike profile is now a copy of the default Road profile but with Ride Type changed to Mountain Bike.
I assume it should be possible to add ConnectIQ fields to multiple profiles?