Select an object and click on the opacity dropdown in our contextual properties dialog. Move the slider on the right side of the dialog or enter the exact percentage you'd like. Adjusting the opacity of shapes can be helpful when you'd like to create a set of related shapes but differentiate (or highlight) certain ones.
Opacity Control is available immediately to all Gliffy Online customers and to existing Gliffy Confluence Plugin customers with the 6.1.2 release.
If you have feedback or suggestions for us, let us know what you think by clicking the feedback button in the top right of the app. Or if you have a support question, email us at firstname.lastname@example.org.