When adding a widget containing a text (for instance, Label widget) to a view, the tooling allows to select the properties file that is going to contain the associated text, as part of the NLS enablement.
When you add new NLS item, it will be added either to the local project or to the global project, depending on the properties file you have selected. If you are modifying the NLS files in a global project, you need to build the global web project before the application deployment to generate the NLS related runtime artifacts. To build the project, please right click on it and select the context menu option ‘Build BTT Project’.