How To Privately Test A Chrome Extension Disabled Because It Is Not Listed In The Chrome Web Store

I have written a simple Chrome extension and tested it using developer mode to load the unpacked extension. It works as expected this way.

Because the extension uses storage.sync API, I would like to undertake further testing with installations of the extension as published in the Chrome Web Store.

The Developer Dashboard for Chrome Web Store provides an option to publish to trusted users only:

Only trusted testers from your developer dashboard can see it. You can also include members of a Google Group that you own or manage.

When I publish this way the trusted testers listed for my dashboard can reach the extension and install it from the Chrome Web Store. However, the extension is always disabled upon starting Chrome:

This extension is not listed in the Chrome Web Store and may have been added without your knowledge. Learn more

We, my testers and I, have not been able to find any way to enable an extension disabled by Chrome. Is there one? If not, the entire exercise of an "unlisted" publication mode seems pointless.