Alexander Deliyannis wrote:

Can Bonsai export tab-indented text outlines? Then you should be able to use its
outlines with quite a bunch of programs, including mind mappers.

It can export CSV, txt, HTML, XML, Bonsai Palm OS, MPX and RTF.

I read that it can
import but not export OPML which is the other popular outline format.

Carbonfin provides an add-on file now which adds OPML export to the Bonsai file menu. So the process with the iPad goes like this:
1. export Bonsai file as OPML on the PC.
2. log on to Carbonfin website and import OPML file.
3. hit the sync button in Carbonfin Outliner in the iPad.