Classification node cannot be deleted due to other classification nodes

 
 
Error:
This classification node cannot be deleted because it contains other classification nodes.
 
 
Explanation:
The Own classification consists of a maximum of 4 layers. When a classification layer that still has layers below it is removed, this error message is shown on the screen.
In other words, deleting a classification layer on the 3rd level, for example, is only possible if all the underlying 4th level classifications are deleted first.
 
Solution:
First delete all underlying classification levels and only then the level that was to be deleted in the first place.    
 
 
Wrong: Under the 3rd level classification layer "Codes" is a fourth layer: "Codes" present
 
Right: The 4th classification layer "Codes" has been removed first, after which the third layer, classfication layer "Codes" can be removed.