There should be some visible indication when pressing the modifier keys (ctrl, accel, shift, ctrl+shift, and any that I have missed) in either the address bar itself, or the address bar results (if the keys are not harmonized) to indicate the action that will occur when pressing enter or clicking on results.

Some of these already exist - for example, if a user presses ctrl or shift when a "switch to tab" result is highlighted, the tab badge is removed from the result.

This should be updated to include a new window badge, a new tab badge, and a background tab badge, depending on the action that will happen when navigating to the page.

This is a good idea! We can bring it up in the next UX meeting.