Operation & is not supported in this area of the screen

What causes this issue?

You selected an operation for which the cursor position is taken into
account.
The cursor is currently in an area of the screen where the selected
operation cannot be carried out.

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?

Error message extract from SAP system. Copyright SAP SE.