[AlanYx]

I'm also a huge Ecco fan and definitely understand your motivation for creating Crossline, but the particular features you mention aren't really ones where org-mode is currently lacking, especially given org-roam.

Where I think org-mode is still somewhat lacking compared to Ecco is in being able to display the same item in multiple places in an outline and be able to edit any one of them (as well as the whole column UI for setting that up easily). But there are solid moves in that direction, e.g., the org-transclusion package is now pretty decent. There's also another more recent one whose name escapes me.

[Rochus]

Crossline supports true "transclusion" links, so you can e.g. compose outlines from existing outline items with navigable forward and backward references; this is very useful e.g. for specification authoring.