For example i want to convert the following shape :
to a group of paths so i get path points in all edges.
Extensions → modify path → convert to dashes does exactly what you want.
You could always use Path -> Stroke to Path and although that would convert the shape into a single path it does give you nodes on all edges like you asked for.
There are two ways to convert dashes, which get different results:
With this method, in the result, each dash will be a closed subpath with 4 corners, no stroke, and fill color equal to the old stroke color.
With this method, in the result, each dash will be a unclosed subpath with 2 endpoints, no fill, the stroke style remains the same, except the dash style will be solid. The "Path>Object to Path" step is essential because the "Convert Dashes to Path" will not work on an object like a circle that isn't technically a path.
For my use-case, I wanted #2, but I can see situations where #1 would be preferred.