E: This node combination is not permitted here (see long text)

What causes this issue?

This node combination is not permitted here.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Combination rules for the second hierarchy level:
- All features are allowed just one node if the node is of the
decision operation or subfeature access type.
- A main feature is also allowed just one node if the node is of
the program access type. Furthermore, a main feature with field
return is allowed just one node if the node is of the return
value type.
- The error operation, root, and field value node types are not
permitted here.
- Two nodes are allowed if one of them contains a debugging
operation.
- A main feature with table return is allowed a maximum of 36
nodes if all of the nodes contain return lines, or a maximum
of 35 return lines and just one debugging operation.
- A subfeature is allowed a maximum of 36 nodes if all of the nodes
contain return lines or program accesses, or 35 and just one
debugging operation.
Combination rules for field value nodes:
- The field value node must have a node child.
- The node child must not be of the field value type.
- The field value node can have just one node child if the node
child is of the decision operation, error operation, or subfeature
access type.
- A field value node for a main feature can also have just one node
child if the node child is of the program access type. Furthermore,
a field value node for a main feature with field return can also
have just one node child if the node child is of the return value
type.
- Two node children are also allowed if one node child is a
debugging operation.
- If a main feature has table return, a maximum of 36 node children
are allowed if all of the node children contain return lines, or a
maximum of 35 return lines and just one debugging operation.
- A subfeature is allowed a maximum of 36 node children if they all
contain return lines or program accesses, or 35 and just one
debugging operation.

Error message extract from SAP system. Copyright SAP SE.