The original discussion in T12144 is kinda convincing to me, although it's mostly convinces me that the term "milestone" doesn't match these objects.

tl;dr:

• "milestones" are subprojects that are strictly ordered in time, like "sprints" - they may one day be automatically created, etc.
• so they track not "progress to a goal" but "ordered work chunk", like "week"
• other then that, they're just regular "subprojects", and users that ask for "reordering milestones" should just use subproject.

To me, the term "milestone" means "X is done/ready", and by extension, "the collection of work that needs to happen so we can say X is done" - and this isn't time-based but content-based.

So maybe we should:

1. Add some tooling to convert milestones to regular subproject / subproject of a new "type" that's visually distinct, but otherwise is basically a "subproject" - for users that were expecting this behavior.
2. Rename "milestones" to something that's more obviously time-ordered ("sprint"? what other names people use for this concept? do they call it "scrum"? "month"?), with possible start- and end-dates. These can't be ordered normally, but maybe we can allow editing start/end dates and have that reflected in the UI.

I feel like the idea behind milestones being strictly ordered is from the viewpoint that milestones are sequential "events" that happen in development one after another in a given order.

Things like "Product Proposal" "MVP" "Incorporating Feedback" etc. would be an example of milestones that happen sequentially.

Version releases would be another example of milestones that happen sequentially.

In essence, IMO, MIlestones the way they are is correct and don't need renaming, but we need a different kind of object to group objects related to things like features, etc. - I suggest we take an example from GitLab and use the name "Epics" for such groups.

Also, this is fairly similar to T15082. Having Epics would probably also resolve that.

If the users want to use milestones instead of subprojects, can they not change the language settings to Pirate English or something and go from there?

FWIW even in the case the milestones are strictly ordered, it's incredibly inconvenient to sort out a situation where you need to add one to the middle of the list - forcing the user to rename a bunch of them to get things straightened out.

For the records, Wikimedia has a downstream custom patch written by 20after4 in https://phabricator.wikimedia.org/rPHAB042685bdf63705ff527a04f4987bdb70209bbe69

Thanks. I think we should mark this Task as duplicate of T15082

In T15127#3188, @golyalpha wrote:

Also, this is fairly similar to T15082.