There is also the ‘cost’ of slowing the app down and not doing stuff in real time
That's a great point, Dave - I am so used to having to render effects in my desktop NLEs that I forgot about the real-time nature of LumaFusion. Of course, as the effects become more complex (like noise reduction and optical flow) it's difficult to keep to real-time and some sort of pre-composition must be done. Most people using LumaFusion are used to exporting short clips so that they can be re-imported to then be used in more complex scenarios. It's hard to manage that type of workflow as the complexity of an edit increases but for short productions it quite manageable...
I would love to have sub-folders for my project lists so that I could group projects together (useful for having a main timeline along with sub-projects used for pre-rendering, for example).