This may be a separate issue, but I frequently have issues changing node numbers of existing piping elements in the model.

Clicking in the "From" node places a cursor in the "To" node field, but allows me to edit neither.

For whatever reason, it's tied to the fact that the window is docked and pinned. When I "unpin" it, and "repin" it, it refreshes the UI to allow me to continue normal usage.

Perhaps this helps.