@pentool I understand that you need a tangent mode for the Line tool,
or maybe a separate Tangent tool.
I did say it's not exactly what you want but I posted this because it could
come handy.
Andโฆ here's another method that could be useful โ not exactly what you need butโฆ
add a node to the shape anywhere you want (the green point in your drawing);
draw a line with the Line tool;
enable 'Snap to Shape' and 'Snap to Points' in the Snapping panel;
pick the line with the Collider tool (fourth tool in the toolbar) and snap it along the shape, orโฆ
snap it to the node you just added (to this one it will snap perpendicularly, but
you can rotate it 90ยฐ)
Again this is not drawing a tangent from the red dot to the green dot, but it's good to know.