The transation is obsolete, use transaction SE43 instead

What causes this issue?

Report trees are obsolete. They have been replaced by area menus as of
release 4.6A. This is why this transaction is no longer supported.

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?

Use transaction SE43 for the area menus.
If you still need report trees that have not yet been migrated, use
transaction RTTREE_MIGRATION to migrate them. For more information on
this topic, refer to Note 205771.

Error message extract from SAP system. Copyright SAP SE.