The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.
Workbench provides options to use both Basic and Advanced Editors. You can set this option as the default from the Tools > FME Options menu, or as required by clicking the Switch to Advanced button on the transformer's parameters dialog.
For example, you want to combine the park name and area attributes into a single label:
Connect a StringConcatenator transformer. In the Basic Text Editor, select the attributes to concatenate, and constants and a New Line to complete the label:
For information about supported functions for manipulating strings, see FME String Functions.