Scanning and inspection is a feature to find hard-coded strings and missing keys in the project, a custom scope or other places in the project tree.
Right click in the Editor | i18n Ally Inspections | "Check the current file"
Right click in the Editor | i18n Ally Inspections | "Check the current directory"
In the Project tree, select files and folders, then right click and select "Check selected with i18n Ally"
Precise scanning configuration is available at the Main menu | Tools | "Run i18n Ally inspections…"
Supported on every source.