Install Module: save and auto-highlight previous URL for usability.
This is a trivial usability improvement, and a minor parity issue between the top URL field and the bottom installation location field.
1. Help > Install Module...
2. Install a module from URL to any location.
3. Help > Install Module... again.
URL field is empty, but previous install location is populated.
URL field is populated with previous path, and auto-highlighted for easy delete.
This matches the saving of the installation path value at the bottom of the Install Module window.