Yes, Floating topic does work... initially.
The problem you will experience is that you may move the floating
Topic, or another topic to close to each other and they will link
together unexpectedly.
The "Float" can only be controlled by selecting the Floating Object
while using the Shift key. It is very easy to forget this action,
which will often result in unexpected links that you must then fix.
I would actually call the implementation of FLOAT a BUG in XMind.
First: The rules are not well documented.
Second: "Floating" is NOT a property of the Object, It is controlled
by an "action" (select & Shift). An objects FLOAT characteristic is
determined by the spatial arrangement (closeness) of objects, and the
users "action" of a move while depressing the shift key. Get too
close to another object without using the "Select & Shift" key
combination and they link.
FLOAT should be implemented as a property of the object so that once
set to "float" the object will not link to another object until the
user turns the property OFF, or performs an explicit link operation.
In addition there should be a property to "fix" the location of an
object. This property would allow user control of the object
placement in the map. If set to "fixed" the object would be placed at
a fixed location and would not allow the map to automatically move an
object. The object would be "fixed" at a location until manually
moved or the property is set to "off".