You can drop various kinds of files onto an open Scapple doc to import text and break it into separate notes on a delimiter you specify. See section 9.1 of the Scapple manual.
However, such import is just bringing in note text. It is not trying to recover tree structure as you would, presumably, be hoping for in this case.
I don’t know of a way to get a structurally intact mindmap imported into Scrivener. I would love to find out there is one, though!
True, but on the other hand, Scapple understands nodes and connections, and so it is unfortunate that it can’t import something with existing nodes and connections — such as the return delimited & tab structured outline text one can pull out of hierarchical mindmaps.
Katherine has a good point though. Because It is freeform, working in Scapple is very different than working in something like Mindmeister. It doesn’t assume any sort of tree structure, and you don’t get the kind of automatic node placement/shifting you are used to there. I use both mindmap software and Scapple, but find them useful for quite different purposes.
You can import some mind map formats into Scrivener, which is hierarchical though. And you can drag note cards between Scrivener and Scapple. Maybe try doing that with a blank Scrivener project and a blank Scapple project, and see how it goes?
But, though the Binder of a project is itself hierarchically structured, when you drag the cards over you just get the nodes (cards), not any connections representing that structure.
If the mind map software’s OPML export creates a hierarchical structure, then yes, Scrivener will replicate that. But if – as in Scapple – the “connections” are just lines on a diagram, with no semantic content, then Scrivener has no way of knowing what it should do with them.