Switch a drawer back to auto-sizing to free the fixed-height constraint

Turn off a drawer's fixed-height switch so it returns to auto-sizing and another drawer can take a fixed height.

1. Each drawer has a fixed-height on/off switch next to its height field.

2. Turning the fixed-height on/off switch off returns that drawer to auto-sizing.

3. Turning the fixed-height on/off switch off frees the constraint so a different drawer can be given a fixed height.