LibreOffice Draw import all connections in VSD file as figures. So it make changing existing scheme impossible. Demonstration: https://drive.google.com/file/d/0B0nwzlfiB4aQNDVsc2FXOUtsc2c/edit?usp=sharing
Example VSD file: https://drive.google.com/file/d/0B0nwzlfiB4aQRWY4R0pWRHNfVE0/edit?usp=sharing
That was a known limitation of the formerly used libwpg API. librevenge has support for connectors, but nobody has updated libvisio to take advantage of that (and libodfgen to produce appropriate ODF output).
*** This bug has been marked as a duplicate of bug 56959 ***
Created attachment 152732 [details] Example VSD file