I can't remember in which version that tool came out. If it's not in V3 then you would need to do it by hand using node editing. Select the vector you want to to work on a press N to go into node edit mode. You can then use the right click menu to choose various options (or press the short cuts keys) to change the type of the spans and nodes. It's not easy to do which is why the tool came out.
It's well worth upgrading to the latest version. There have been many worthwhile changes and additions since V3.