In my case, there are about 30 overlaid features. How do I select all and edit them at one time? I want to reshape the features, mainly using the node tool to reshape a straight line into a (fake) curve one.
To do this you need to define how the co-located features should relate to each other in space. That is their topological relationship in terms of their geometric construction. In ESRI software this is called a topology.
I don't think any of the open source projects have this ability yet (I would love to know if they do!).
You can work around these type of problems by constructing temporary features and then using batch geo-processing to clip/intersect the features you want to reshape.