I'm having an issue where I have completed the first set of levels in Deeper Dungeons, but then trying to scroll down to the next set, it immediately goes to the last level, and I cannot stop it. Is there any way to make it scroll slower?

Use the very tip of Horny face's head-horn (the right side one I think) as the click pointer, if you're not already.

The only way I can make the menu manageable is to not "scroll" but click. So hover the tip of horn over the scroll bar button and click and lift finger off button as fast as possible again. Only once. Then the list tends to go down by a few/several level titles instead of all the way to the bottom willy nilly.

Repeat as necessary to get to the level title you want. If you start using the editor and have a lot of your own levels in the list as well, sometimes you have to click down, down, then up again if it overshoots.

I tried that, just clicking on the bottom arrow to go down, but it insta goes down to belial and that's the only level I can see, then going back up again just shows down to abaddon.