One of the unique features of Lokalise is the ability to use similar keys across different platforms, thus reducing the translation work amount to be done by translators. Once you import or add keys, they need to be assigned to one or several platforms (e.g. iOS, Android). Assigning key to a platform basically means including the key in the export routine for the chosen platform. For example your key APP.TITLE needs to have the same translation in both Web and iOS projects. To assign multiple platforms, either click key name in editor (bringing up key editor dialog) or just click platform icon in project key view.
Different keys for different platforms
Coding for different platforms usually involves different naming schemas, for example iOS coders prefer "LoginButton", while Android coders are keen for "login_button". Lokalise has the solution for the never-ending battle. Enable "Per-platform key names" in project settings, then once you add a new key (or edit the imported one) there is an option to set unique key name per platform.
Hidden and archived keys
If you are not done editing your original translation, mark the key as "Hidden from contributors" so contributors can't see it and don't start the translation. Note, that other project owners will see this key and it's translations.
Optionally, you may want to archive keys so they are not visible in statistics, export, search and similar. Archived keys can be found by choosing "Archived" in Filter. In order to archive or unarchive keys, select the desired keys in editor view (by ticking a checkbox on the left of the key) and choose appropriate action from the floating box.