Using imessage deleting message When deleting imessages on my mac, I want to press space bar so that i can quickly click on "delete" however tab doesn't work and I can't seem to focus on the pop up that has two options "cancel" and "delete".  Basically I would like to press tab and then press the space bar to delete the imessage.
Go to System Preferences -> Keyboard
Select the Tab "Shortcuts"

At the bottom there is the option "Full Keyboard Access". Switch that from "Text boxes and lists only" to "All controls".

Then you can use tab + space to select the Delete option in the dialog.