When adding new nodes, user needs to be able to choose how many output ports it will have or what color it will be or what it’s name will be. Form editor is not necessary. Any method to provide these features will be efficient.
The user could choose the properties before creating the node in some custom HTML.
The user could create a node and a modal dialog could allow customizing the node.
The user could create a node and at any time could customize the node via additional commands, such as via a context menu or a Data Inspector or some custom HTML.