With the edit in source code feature, the user can navigate to the code fragments in the annotation file where the related annotation is defined.
To find the Edit in source code icon in the Property Panel for editable and non-editable properties, locate the annotation tag, and click on the 
(Edit in source code) icon next to the text field. If multiple definitions are present, a pop-up window with the options appears, and you can click a particular file to see the definition.
Multiple definitions pop-up window are only available in Visual Studio Code. Only the first annotation is displayed in SAP Business Application Studio.
There can be more than one way to configure a UI feature on a Fiori elements-based application. Some ways will be too complex for the Page Editor to interpret. In those cases, the respective field control (dropdown, input field), including the Edit in source code icon is not rendered in the Properties Panel. Instead, the Edit in source code link is displayed with the same functionality as the icon. You can then use this link to edit the property directly in the code.