POEditor currently supports pluralization for the following localization files:
If you import a file that contains strings with plurals enabled, they will automatically show in the POEditor interface, in accordance with the target language.
The plurals from iOS XLIFF files are structured differently from the plurals from the other supported file formats. For this reason, it's not possible to import plurals from iOS XLIFF and preserve them when exporting to another supported format, or viceversa.
You can also manually enable pluralization for a term in the Terms, in the Attributes of each term. The actual plural forms are visibile only in the translation pages.
A term with pluralization enabled will have a separate tab for each plural form above the translation box. Here's an Arabic localization page:
In cases such as that of Chinese localization, when the localized language only has one plural form, POEditor displays the translation boxes without any plural tabs.
You can read more about plural rules at the Unicode Common Locale Data Repository: http://cldr.unicode.org/index/cldr-spec/plural-rules