I have a JS error in browser console. Please, hence the tracker item.
Thanks for the hint about the "scroll wheel". I am using a pen/tablet! ;)
I am not sure, if the error is also responsible for the missing "alternative". Can't remember exactly how it looked in the past. I believe there was a way to switch to another appearance and selection method. I can't remember that I have had any problems with this dialog.
BTW, if the current selection and scrolling is the ONLY way to select the template... it has to be improved.
The thumbs list should definitely have a scrollbar!
If there is no UI to scroll the content, a touch/swipe script would be the better choice.