Both .ftw and .ftb files originate from Family Tree Maker genealogy software, so if any kind of ftw to ftb conversion or export is possible, it would be done with this software. We have not found any particular information about such export, but generally speaking, export of genealogy data is usually possible.
In any case, if you have issues with export of Family Tree Maker files, it would be best to contact their support or some online community for help.