Parallel and In-series Phases with Dependencies on Selected Lines

I was trying to set up a new release template with phases to match our typical release management steps but ran into difficulty because the Aha! release phases are set up mainly to occur sequentially / in-series, but our list of items for a release are a combination of things done in parallel and in series---a combination of things that may or may not be dependent within that list of things that need done prior to the release.

I would love to be able to capture the list of things that need done that don't happen necessarily sequentially for each release while still using a release template. Specifically, I would like release phases timeframes to be auto-calculated by using a selected line item and not just dependent on the timing of the item right above it.