Diagrams.net (formerly known as the draw. IO) is open source free flow chart drawing tools, very good, but given the default template didn't mind mapping,
Research and found that it support to draw mind maps:
(1) create a blank project, "senior" in the graphic panel on the left of the plate in the last few drawings is a mind map element,
Are: the Central Idea, Branch and Sub Topic, OrgChart, Organization, Division, Sub Sections,
(2) I usually choose Sub Topic for drawing, graphic box in the upper left + - number, click can expand and collapse, it to reach the effect of mind mapping,