I want to create boxed rehearsal marks that show times such as 0:47 and 1:30. Is there a way to do so?
Yes - those are called Markers in Dorico. Go to the location you want and type ALT-SHIFt-M Alternatively you can create them by clicking on the little video clapboard in the right side panel, go to markers to add or edit. You can name them / use a reasonable amount of text in addition to the time code.