Seems this didn't get much traction; maybe a post on the list might garner some views? Now that line width clipping is gone, what is your current stance on this change?

Huh, sorry@QuLogic, just notice your post now... (The notification is likely to have sunk in my inbox 🐑)

I still think that this could be an interesting feature, but it needs to be better formalized before going any further. I think that it might be worth giving a shot at the the devel-list to try getting traction. I am also wondering about atrick that@anntzer made in#10244 .

For the moment, simply re-milestoning it for 3.0, with the hope that I will manage to find time to be a bit more active on this in the next few months...

Feel free to re-assign the milestone if you get back to this...

Since this Pull Request has not been updated in 60 days, it has been marked "inactive." This does not mean that it will be closed, though it may be moved to a "Draft" state. This helps maintainers prioritize their reviewing efforts. You can pick the PR back up anytime - please ping us if you need a review or guidance to move the PR forward! If you do not plan on continuing the work, please let us know so that we can either find someone to take the PR over, or close it.

I think the main question here is just whether we can find a reasonably syntax for user-specified dashes. My guess is "yes, as long as we don't try to support them in the plot shorthand syntax" (which is carefully designed to minimize confusion between color/marker/linestyle, but even then the introduction of the data kwarg made things awkward as the shorthand can also be data kwarg entries).
If we only want to supportlinestyle="user-speficied", we can always consider having arcParams["lines.custom_dash_patterns"] = {"name1": [...], "name2": [...]} (or even rename that more generically to lines.dash_patterns and move the three standard patterns into the dict as well). (Note that this doesn't need anything too bad on the matplotlibrc side; we can easily support that syntax e.g. with ast.literal_eval.)

So closing for lack of activity, but I think there are ways to revisit this if there's interest.