Currently you can drag local variables to any context, which can cause all sorts of bugs. Create a scope concept for Waterbear so they can only be dragged where they have a valid scope.
Also detect local variables are added to a child block, which is subsequently repositioned to make the local variable be out of scope.
In the process of solving the above issue, it might be worthwhile to look at ways that other block might need something like this.
For example, the break statement can only be within a loop block.
Fixed as part of #239