while this is getting votes, just a quick note that this is already available as a three-step process:
1) use ctrl+x (or cmd+x on mac) to cut a subtree
2) Use File→new from clipboard (potentially in a new mindmup window) to create a new map from the cut tree. Save it and copy the URL from the browser
3) paste the URL into the original map as a new node – this will link to the new map
An error occurred while saving the commentGuillaume Jambet commented
Strikethrough the whole text node would be really great as it helps you use a map as todo / done / not done ...