Can't use the tool, can't add the definition, don't see any save buttons

(Responding on the assumption that you were trying to add a language section but the button wasn't available.) The "Add language" feature is actually part of Tabbed Languages, not editor.js, but it depends on editor.js's section- and definition-editing tools, so it won't load unless those are available. Unfortunately, the current default-on Tabbed Languages admin-only trial relies on using a gadget, so it loads a bunch before editor.js, and when the tabs are being built the tools aren't available, so the "Add language" button isn't added. If you turn off the trial in Special:Preferences and enabled TabbedLanguages and the tools through PREFS or the button that's available in several places (actually, given that you seem to have editor.js enabled already, you probably have both enabled like that already?), then it will work right. (If the problem you're experiencing is something else entirely, I'll need more information in order to fix it.)

Thanks for the reply.

I have had TabbedLanguages enabled for a while.

Let me describe in detail what I' trying to do. It may be a mixture of tools required, I don't know.

1. I open the entry عروس (ʿurūs).
2. Click on "Add language" link below Arabic.
3. Type "Persian" in the window and click "add"

Persian is now visible. In the new window type "Noun". Then preview. Editing transliteration is not possible at this stage but now I can see عروس as the header.

Clicking on definition edit (with a small pencil icon) doesn't allow editing. "Add gloss" doesn't work either - the window is there, I type "bride" but clicking "add" doesn't do anything.

This is where I get stuck. I can't even save what I see - the language heading (Persian) and عروس.

Got a bit further but still can't save changes.

Hm, looks like another bug from the reformatting of the category section in MW1.18...

Does it work now?

(Note that the save button is in the top-left corner of the screen, the same as for other WT:EDIT tools.)

Much better now, was able to save. There was no button previously.

Issues:

Althouth I selected "Noun", it has only created the correct header but as you see, the {temp|infl}} didn't have it.

This is what it looked like before I manually edited it:

==Persian==

===Noun===
{{infl}}

# bride

At the moment the tool doesn't have a good way to generate inflection lines. The line has to be inputting "manually" by entering wikitext in the field under the Part of speech box, or if it's left blank it defaults to {{infl}}.

Thanks for the advice.