summary of predefined names, routines, macros?

Sure, but it can get fiddly. For example, you may not know what type digitalWrite returns. Or what type arguments it takes.

I just wrote a little helper function that reads the tags file into a Lua table, and then displays them, filtered on what you type:

Then when you choose one it opens Crimson Editor for the relevant file, copies the chosen word to the clipboard, so you can search to find it inside that file. Now that should save a bit of time!