Please bring back the one-click way to duplicate a value from one input field into another for dialogs.

This was available from version 8 through CS5.
Make it a toggle in Preferences.

For example, if i wanted to make a square 100mm x 100mm I would select the rectangle tool (M) and then click once in the work area... the dialogue box would come up... I would then only have to enter 100mm into the Width,
then click on the Height descriptor (not the white entry portion) and my dimension would be automatically duplicated in the entry portion of the height dimension.