tried this all afternoon in Gimp and Inkscape

all the usual tools like ofnut's seamless helper or Tav's Inkscape recipe for making tiled patterns didnt help

so lets say i make a grid of paths, rotate it by 45°, then add nodes and jitter them
how do i make this grid seamless, so it tiles continuously ?

It can get very fiddly, but the cleanest way can be done by hiding one tile partially by another one.

For example, it was used in these spirals.
Or a more recent and tile-looking example:
https://openclipart.org/detail/210796/seamless-triangle-tiling-by-lazur-urh-210796

Which later was used to create a kaleidoscope.

Probably the solution used in that triangle tiling is far from the simplest and not so trivial at first glance.
It was made from the centre, and the outer rectangles can be deleted, the pattern is still seamless.

Will provide a more straightforward example soon.

sorry Lazur, i have no idea what your example means

i think i just found the solution, in this video:
https://www.youtube.com/watch?v=I9nM155skDI

the secret is getting the base tile into the middel, instead of the left top