Hi Jochen,
I find the sinter pool double line doesn't give a very good result.
In my opinion:
- the separation between the plaine line and the dashed line is far to wide
- the dash length and inter-dash space are too large.
- the dashes are not a dashed line but tangent dash to the plain line, which produces ugly results with bending lines

Attached some examples
in red = sinter pool double line.
in black = plain line + 1/2 dashed line which is better but still improvable using 1/4 dashed line I guess.



would it be possible to get an improved feature?

Definitly better than it was before but one problem remains. I draw sinter pool with wavy line, and if a wave has a slightly "sharp" angle, then the dashed line behaviour isn't good and give stranger render : the dashed line crosses the plain line. Same behaviour is observered with entrance double-line and show clearly the issue.

Is there something that can be done to prevent this? using a buffer instead of an offset?

this is great thanks very much!