Drag to vertically adjust the connector line between keyframes. Use control to add a keyframe.

V25.1.0 (beta) introduced a new behaviour in the sequence panel whereby a clips opacity can be adjusted directly by pointing to a particular area on the clip and dragging up or down. This is super annoying because most of the time, all I want to do is select and move the clip. But if I don't click the clip with high precision and avoid the opacity adjustment area, then I will unwittingly adjust the opacity instead of moving the clip.

PLEASE, remove this behaviour and make it available only when "Show keyframes" is selected in the sequence panel settings menu.