I don't think adding monolingual text support will help. They appear to be trying to add labels to items, thinking that they are lexemes.

Hi all
I was trying to add Gamilaraay label to exsting page buruma, if I do want create one, do I need to make new page?

@GerardM what's your consideration on this request?

@Bluepossum only languages that are in Names.php are available for labels, so if you're requesting that, you need to consult translatewiki.net first.

@Bluepossum Based on your edits, it seems like you are trying to add entries for words, like in Wiktionary. If so, you want to add lexemes not items (items represent concepts, not words). The page for adding new lexemes is https://www.wikidata.org/wiki/Special:NewLexeme. This page is not yet very visible, probably because lexeme support is still very new and missing key features. After you enter Gamilaraay in the language field, you will need to select "mis" from the field which appears above it. It's not yet possible to link lexemes to their translations, so you won't be able to link the Gamilaraay word "buruma" to the English word "dog" or to the item Q144 yet.

Ok from LangCom for monolingual. We could add it for labels + descriptions as well, shouldn't be a problem.

Change 533598 had a related patch set uploaded (by Jon Harald Søby; owner: Jon Harald Søby):
[mediawiki/extensions/Wikibase@master] Add several monolingual languages

https://gerrit.wikimedia.org/r/533598

Change 533598 merged by jenkins-bot:
[mediawiki/extensions/Wikibase@master] Add several monolingual languages

https://gerrit.wikimedia.org/r/533598

Adding a value using the language code works, but the language code is not shown, just a code. This probably requires a change outside of Wikibase software.