In 8.4.0 I am not able to edit the download URL to add a VC variable reference.

The download step either adds a job variable (with a blank name) if one doesn't exist or it uses the first one in the job variable list if one or more do exist.
This happens even if I have the save to variable unchecked, which is default.

This messes up the variable values when the job runs, wiping out the value of the per-existing job variable value if there was one in the list already.