A game project needs to be compiled into byte code and assets converted to be used in the simulator or playdate. Based on my experience this is typically pretty close to instantaneous even for bigger projects, so I never felt it was slowing me down.
Usually I am in my code editor and I have a build script that prepare the pdx and launch the simulator automatically.
But that depends of what editor you use to code.
This is an extension for vs code but I don't know if this is still maintained
Having the Simulator be able to run pdc seems like a really useful feature. I seems so obvious I wonder if we looked at that and found a bunch of pitfalls, or we're just so stuck in our routine it never crossed our minds. I'll file that and mull it over!