I'm not sure about your data, but if it can be exported as an indented list, then you can import it into Leo as a "Tabbed File". This will turn every line in the indented file into a new node whose headline is the text on that line. The nodes will be indented to match your exported data.
By "indented list", I mean a file that looks like this:
item 1
item 1a
item 1b
item 1b1
item 1b1a
item 1b2
item 1c
item 2
Also, I have written a set of Leo scripts that will take a node with such a list and turn it in to an SVG mind map to a maximum depth of two, if that would be of interest.