Until about a week ago (guessing), with the Scale plugin it was possible to set a binding that required both to touch an edge and click a mouse button, however now that feature is missing, only an edge or a key can be set now. The Expo plugin still has this feature, and I think it is important especially for the show all windows mode of Scale, it is way to easy to bump an edge on accident if you have Windows that probably should not be exposed to others in the general area.
Fixed in commit 891f7faab81ada11bd2785f32d6fb7e116a76804.
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.