You cannot create another elementary transaction on the same level

What causes this issue?

You attempted to create an elementary transaction on the same level as
the elementary transaction you selected.
However, this is not possible in the following situations:
If the elementary transaction you selected is the first elementary
transaction
If the elementary transaction you selected is a Bermuda option
(transaction form 63), or if the underlying is a Bermuda option
You can create only one elementary transaction in the next level down.

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

System Response

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.