Hi Guitar Tricks Admin

Add another voice to the OP point

Setting up loops is a royal pain-in-the-rectory.  To get it accurate is way too much of a fiddle.  The simplest coding solution I can think of is 2 buttons

"Set Marker A Here"

"Set Marker B Here"

...or whatever you want to call it. Which would set the appropriate marker to the current video position.  No need for fiddly "enter timestamp for marker" boxes or dynamically changing a "timestamp highlight" when dragging the marker

And god forgive you if you ever make the mistake of accidentally pressing the right mouse button whilst dragging a marker!  You will then never be able to drop it, the only solution is to reload the page

But having one or even multiple links to set markers for appropriate follow along bits in lessons would hugely benefit your site imo