I understand one can go to Edit → Remove Rests but the documentation  details what I assume is the “correct” procedure. The issue is, I can’t for the life of me get the a rest to hide. Here is a simple measure in 4/4:
Now, the goal is to hide the 1/4 rest on beat one. So I highlight the 1/4 D on beat two, go to Properties → Notes and Rests and click enable Starts Voice. Problem: It doesn’t allow me to enable it. Basically, that whole procedure with Starts/Ends voice doesn’t work (clearly I don’t understand it).
Can anyone enlighten me?
 Hiding/Showing rests
You are using the Dorico 1 manual, probably because you searched for the issue on Google, which prefers the older files because they have been around longer and therefore have more clicks.
For the version 5 documentation, try
… Could have sworn I searched directly in the documentation itself – clearly not. In the meantime, I figured out that the Ends Voice option actually does work but it seems easier to just use Edit → Remove Rests.
One way to check is to note the v1 in the link address.
Edit>Remove rests really is the simplest method (it automatically sets the correct start/end voice parameters in all affected voices). Experiment with different selections to understand how it works.
Finding the starts/end voice parameter is only useful if you need to recover rests you have inadvertently hidden!