Hi @TDhondt,
If you mean that you’d like to track conversion rates of deals that move from one pipeline to another, then no, this is not possible. Generally, HubSpot expects deals to stay within one pipeline and this is also a requirement for reporting, as you already noticed.
As far as workarounds go, you could either include all stages within one pipeline (so that they don’t have to move between pipelines) or create a new deal in the second pipeline after a deal closes in the first pipeline. In any case, you won’t be able to see conversion rates for one deal across/between pipelines. This is unfortunately not possible.
Best regards!