Following update2, engines no longer show their @keyword when the "@" is typed in the address bar. As a result, we should show all the user's engines in this list, regardless of whether they have a keyword assigned.

We currently cap the number of engines shown for "@" to maxRichResults (default 10). en-US has six search engines by default and we're adding three more results to this view in bug 1675048. We should increase the maximum number of results shown for searches for "@" to max(20, maxRichResults).

See related discussion in bug 1526983

For the list we should probably also respect the checkbox, if the engine is unchecked then not list it. Mostly because in bug 1681512 we'll make tab-to-search respect it. Verdi explicitly said unchecking an engine should never suggest it.

I spoke to mconnor about this bug and bug 1526983. He would like to see a UX spec showing the change so it can be reviewed with by BD, since this would change how we present search engines.

The investigation work is complete, a test build has been presented to UX and PM, there are further ideas to investigate and integrate, thus I filed Bug 1691076 and I'm closing this as incomplete.