Non-modifiable rows are caused by locked nodes

What causes this issue?

In the "Assignment to Article Hierarchy" maintenance view, some of the
nodes listed may be locked. To avoid inconsistencies, the rows concerned
are locked, which means that the main assignment cannot be edited.

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?

If you want to edit one of these locked nodes, you can use transaction S
M12 to view the lock entries. In the Table Name field, enter
WRF_MATGRP_STRUC. Here, you can find out who is locking the node and can
contact that person. Do not delete the lock entry manually as this could
cause inconsistencies.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.