Using actions without a target is pretty awkward at the moment, requiring either a right click on the quest toolbar button, or macro use (via the quest log). There should be a clearer way to use actions during a campaign even when no target is selected. Showing the actions toolbar at all times when the campaign is active might be an easy workaround for now.

Until work is started on the objectives tracker which could hold the actions buttons in the future ?

Actions are currently hooking the TRP3 target frame, so this would probably require moving them to a new frame. Not sure it's worth it until campaign tracker rework.