The formula was composed up to the first syntax error

What causes this issue?

You have attempted to exit the insertion mode. This is only possible if
the formula has no syntax errors from beginning to end. If this is not
the case, a new insertion mode will be opened before the first syntax
error. You can remove the syntax errors at the new position by entering
or deleting the subsequent formula symbols.
Afterwards, you can again attempt to end the insertion mode.

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?

Error message extract from SAP system. Copyright SAP SE.