According to this tutorial, you can change the project framerate [in DaVinci Resolve]
Sure, but that's not the problem. There's no existing timeline that needs to be changed. If I want it to process the video at X fps then I can just create a timeline with X fps. But I want to have it process the timeline at Y fps and then output it at X fps. So the timeline needs to be at Y fps, not X fps. It's just the end result that needs to be resampled to X fps. In the tutorial you linked to the video will still be processed at whatever framerate your output is.
Since DaVinci Resolve can't export in a different frame rate than it's processing the video it would be extremely useful if voukoder could do that! This way one could process the video in 60 fps and then export in 30 fps (perhaps after a tmix filter, or not).
(Apparently the fps filter caused problems with some Adobe program, but Adobe can already use a custom export fps, so the fps setting could be excluded from the Adobe connector.)