You can resave .mmap to .xmmap files only using the original MindManager tool or perhaps other brainstorming or mindmapping utilities with support of MindManager's format. Used to transform mindmaps to XML based format.
Convert MindManager Mind Map file to MindManager XML map file.
We found 2 software records in the database related to .mmap to .xmmap file format conversion.
Microsoft Windows software - convert mmap to xmmap on Windows
A brainstorm mapping software
Convert from mmap file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned mmap to xmmap. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert mmap to xmmap on OS X
A brainstorm mapping software.