I'm working on a score in 4/4 and would like to insert a half-measure rest in between sections. What would be the most appropriate/readable way to do this? Switch to 2/4 and back, like this:
Well, both of them are readable by someone who knows notation, but the second one is technically wrong, since the bar is now 6/4 and not 4/4. So, you could either change the time signature to 6/4 in your second example (just for the first bar) or use the first example.
I would prefer the first example, because the 2nd one is, as already answered , technically wrong. I would suggest a Fermate-Symbol after the last quarter Note.