@Roman_hruska sincere apologies for the late response. We actually had taken in your entire example and discussed this in lots of detail internally. Building similar examples out to see what the behavior was and if there’s anything we could do to address this in its current version. Unfortunately… the short answer is: currently not supported in Preview by the Connector Builder Activity Pack. Technical reasoning behind this is that we are flattening some of this detail behind the scenes that then gets you into the problems you indentified once moving it to the Activity Pack usage within Studio
The better news is… Soon (targeting end of December / beginning of Jan) we 'll be generating a specific Activity Pack for your connector that you created through Connector Builder. It’s going to be on the moment you “Publish” within Connector Builder. This gives us technical advantages of creating classes matching your setup, request & response models, rather than doing everything Just in Time in the Connector Builder AP and hitting limitations as these.
FYI and in full transparancy - that’s bringing what we do for our official connectors right into Connector Builder
Once we have that update out, we’ll announce this here / preview program and will be a good way to test this