As you are doubtless aware, FMOD Designer’s engine designer tool is an auditioning tool only; It’s slightly more convenient than manually adjusting the parameter values of your event while auditioning, but adds no other functionality. It was originally added at a specific user’s request, in a time when FMOD was being used in a large number of racing games. However, we soon discovered that we had underestimated the variety of ways in which an engine can be modelled. While the Engine Designer worked well for the designs of the specific user who requested it, the vast majority of users were designing engines that worked completely differently in a myriad of ways. As a result, the feature we had developed was useless to all but a few of the users we had intended it for.
We learned from that mistake. Since then, we no longer create features that only work in highly specific situations; Instead, we aim to create tools that are flexible and adaptable, so that people can come up with uses for them that we never imagined.
To answer your question, we do not plan to add a Designer-style Engine Designer tool to FMOD Studio. Instead, we will continue to add features that make it easy to audition all manner of events, such as the API capture and playback feature included in our recent release of 1.06.