This functionality is provided since SAP NetWeaver 7.3 EHP1 SP14 and higher as well as SAP NetWeaver 7.4 SP08 and higher.
The text symbol exists in the text pool.
You can edit text symbols in order to modify the text content or the maximum length.
Example
You want to update the text content of a text symbol:
greeting = 'hello'(B01).
The text symbol is adopted in the text tool and activated.
Example
In the source code editor, the text content is updated:
greeting = 'good morning'(B01).