I am on Win 7 and just tried manual syncing of clips against a script and it works just fine. Drag clip onto script, highlight take(s) (lasso them), then hit the record button (top left in window with a dot). The clip line turns green and will start playing. As it plays, click the line that matches on the script. Hit the space bar to stop. Marks appear in script.
One issue I noticed and brought up in beta is that the icons at the top of the page have no color… the record button used to be red, and flashed when the the syncing mode was active. Also, the color span selection does not display what is selected. You do have the ability to shift sync positions, but all of that is manual now as you know.
Script Based editing (without the phonetic sync technology) has not gotten much attention in many years, and 8.3 does show further regression as noted.
Michael