My intention was to add 12 new nodes (points) each at equal intervals between the 4 existing nodes on a path (circumference) of a perfect circle. Another words so that each point is at each tip of an invisible 16 sided regular polygon inscribed in the circle.
1 Making a circumference guide with 4 line guides in diameter rotated at 45° was a promising star, but new nodes would not snap to it at all. Making same lines as shapes instead of guides seemed to work as nodes did snap to points.
2 Rotating lines both as guides and shapes at 22.5° caused them to slightly shorten no longer fully reaching the circumference.
3 Making a 16 sided regular polygon instead to avoid rotation oddly resulted in some of its tips not fully reaching the circumference either (other than at 45°).
4 Rotating the very circle shape 22.5° to add nodes and snap them to points of 45° lines caused the circle to slightly change size. As well as new nodes slightly changing the shape of the circle when manually dragged to line points from very nearby.
5 (Additional) Rotating 1/2 of a circle at 22.5° made it slightly shorten in width as well.
The goal was to manipulate the circle so that some nodes come closer to the centre but at pre-planned and precise distance from it. The coordinates as well seem to be going unnecessarily crazy and showing correct values only after selecting another shape and coming back to the former.