Localization hints is a feature that enables the preview of translations from the language file in the source code.
The feature can be toggled via Ctrl + Shift + , (Cmd + Shift + , in MacOS),
right click in the Editor | i18n Ally Inspections | "Enable/Disable localization hints"
or toggling the checkbox in Preferences/Settings | i18n Ally | Feature flags tab.

Supported on every source.