It would be very practical to be able to set your own screen size. 1. with Safari on macOS 2. Go to a website 3. Starts Responsive Design Mode 4. Click on the top couple of numbers representing the viewport size. Expected: The numbers are editable and can be saved. Actual: The numbers are immutable. This is important when dealing with some webcompat bugs when the issues happens only in certain circumstances of form factor
<rdar://problem/97361469>
Note: I noticed you can resize by doing drag and drop on the sides, but this is less precise, and less quick than setting the right size directly.
The cause of this issue is in code outside of WebKit, so resolving as MOVED.