I basically just mean having a date input like you would in excel where it brings up a calendar and a clock if it’s time – and defaults to “now”

I would love that as well, but I kind of suspect the frontend people will say these things tend to start small and grow into a huge effort. At the moment what we do is the UI is basically plain text and the casting is done on the SDK side.
You can however provide type information and help (you can see it when you hover over the arguments on the right hand side)