I first started using Marked as a teleprompter for screencasting back in 2013. With the right style and the built-in autoscroll feature, it makes a serviceable replacement for some of the (often spendy) teleprompter apps out there.
The first step is to get the Teleprompter theme from the style gallery. Just visit the page on your Mac and hit “Install” to add it directly to Marked.
Once you have the theme, you can start prompting just by hitting the ‘s’ key in a Marked preview. That will start autoscroll at the slowest speed. Use left and right arrows to speed up/slow down the scroll speed. (You can also click and drag on the meter that appears in the lower left of the screen.) That’s all there is to it.
Well, one more thing. As of version 2.5.41 (out for Paddle and Setapp customers, awaiting MAS review), you can add pauses to your script. If autoscroll is an unknown feature that few people will use, then this is a truly obscure one that will probably only be just for me. But if you write your scripts in Markdown (or just plain text) and would like the autoscroll to pause at certain points, you can just add
<!--PAUSE:15--> (where 15 is any number of seconds) in the document. When that line scrolls to the center of the window, it will pause for the specified number of seconds before continuing autoscroll. Even if this feature rarely gets used, it will never get in anyone’s way, plus it was fun to code. I stand by this addition to Marked’s feature set.