Thank you for creating those collections! Since your account's language is set to Spanish, the collection is marked as Spanish as well. When searching collections, set the filter to Spanish and search for "alfabeto" or "griego". The collections also appear if you don't enter a search term but sort by "created".
Currently, the app does not provide Greek as reference language, but it will in the future. Therefore I suggest to create a dedicated Greek vocabulary verse account that can later be set to Greek (e.g. for text-to-speech) without disturbing your own Spanish Bible memory verses. You can do this within your already existing user access.