No entry in TCLO for object &

What causes this issue?

You want to assign a document to object &V1&.
Settings in Customizing (Document management -> Control data -> Key
fields) defined which objects you can assign to documents. There is no
entry for object &V1&.

How to fix this error?

It is possible to link other SAP objects to documents. This requires
other activities, such as creating a screen.

Error message extract from SAP system. Copyright SAP SE.