I Just remembered that these positions used by the menus are also those available to the reveal widget.
- Thus I find these positions in use here $:/plugins/tiddlywiki/menubar/menu, near the bottom.
- This is not what the OT is about, instead asking for hover mousemove event, typically what tooltips are. These and their positions are discussed here CSS Tooltip and can be done in CSS only.
I will raise a related question action on mouseover.