Cannot trigger new AdminUser action in plugin

I’m working on my first plugin, and am having trouble triggering an action. I have this template in the after-user-details connector:

I then have this initialize script:

So the template uses action=(action "mergeInto"). mergeInto is added to the actions object of AdminUserIndex, which then calls AdminUser::mergeInto. From what I can see, this matches the other actions like anonymize, destroy etc.

When I try clicking the button, I get this error:

Uncaught TypeError: Cannot read property 'apply' of undefined
    at e._join (_ember_jquery-5dbd79abddf53926275c73f77dbe61e7351258de8d2e886bf2ce86f144368848.js:57275)
    at e.join (_ember_jquery-5dbd79abddf53926275c73f77dbe61e7351258de8d2e886bf2ce86f144368848.js:57023)
    at c (_ember_jquery-5dbd79abddf53926275c73f77dbe61e7351258de8d2e886bf2ce86f144368848.js:45520)
    at _ember_jquery-5dbd79abddf53926275c73f77dbe61e7351258de8d2e886bf2ce86f144368848.js:17847
    at f (_ember_jquery-5dbd79abddf53926275c73f77dbe61e7351258de8d2e886bf2ce86f144368848.js:42670)
    at _ember_jquery-5dbd79abddf53926275c73f77dbe61e7351258de8d2e886bf2ce86f144368848.js:17846
    at (_application-02da28b6813b1b32a18ca63f17b17a6324621575b9a375552668c1d2444c9dc4.js:44502)
    at n.trigger (_ember_jquery-5dbd79abddf53926275c73f77dbe61e7351258de8d2e886bf2ce86f144368848.js:38862)
    at n [as trigger] (_ember_jquery-5dbd79abddf53926275c73f77dbe61e7351258de8d2e886bf2ce86f144368848.js:36445)
    at e._run (_ember_jquery-5dbd79abddf53926275c73f77dbe61e7351258de8d2e886bf2ce86f144368848.js:57292)

I’m guessing that one or both of the reopens didn’t work properly? Or that the button action isn’t working properly?

Or, this topic suggests plugin-outlets need to manually specify actions in the args, is that true? Is it practical to add new actions like this in a plugin?

I’m thinking it might be better to make a new admin page for this.