How to add more categories to the user interface backend insert mode? Since Gerneral, Strucutre and Plugins are not enough.
You can just change/amend the
Neos.Neos.nodeTypes.groups configuration. See https://neos.readthedocs.io/en/stable/CreatingASite/RenderingCustomMarkup/CustomContentElements.html?highlight=nodeTypes.groups`#content-element-group
PS: You might want to consider using Node Type Constraints more so that there are only the reasonable node types shown at a time.