To open the Rest Property dialog box, you can either select the Object Select icon from the Layout Tab, or if you have a note or rest selected you can hover over the rest and single click it.

The layout tab responsible for your score layout.

Rest Properties

The property dialog box for a note, where you can edit rest duration or change a rest to a dotted rest

There are 2 rest properties.  These properties have a shortcut.

Rest Duration

Changes the rests’ duration if able.  For example, you can change a quarter rest into a 16th rest.  The shortcut to update duration is to hover over the rest, or select one or more rests using the Measure Select tool and press ([) to decrease duration or (]) to increase duration.

Rest Dots

You may update a rest to a dotted rest.  The shortcut to update a rest to a dotted rest is to hover over the rest, or select one or more rests using the Measure Select tool and press (.) to increase the dots, or (,) to decrease the dots.