Is there a way to remove assets that are not referenced on the timeline from the project media list? I often use an old file as a template and delete events from the timeline, but they stay in the project media list.

At the top of the Project Media tab, click the icon that looks like a lightning bolt (remove all unused media from project) and anything not on your timeline disappears.

Button "Remove all unused media from project" im Project Media window looks like yellow lightning.

Great, thanks.