One possiblity is Ctrl-{. It takes three key strokes on some keyboards, but it's memorable as long as it matches the toolbar icon, and not that hard to type.

(In reply to comment #1)

One possiblity is Ctrl-{. It takes three key strokes on some keyboards, but
it's memorable as long as it matches the toolbar icon, and not that hard to
type.

We're almost certainly not going to keep '{}' for code (especially as there's <code> and <syntaxhighlight> that need to be distinguishable), but it's a possibility.

fred wrote:

When is this planned? I was about to write that enhancement proposition as well when I saw this ticket.

My personal preference would be to have a shortcut near the ctrl tab on the left of the keyboard.

Change 160174 had a related patch set uploaded by Jforrester:
Add keyboard shortcuts for strikethrough and code annotations

https://gerrit.wikimedia.org/r/160174

Change 160174 merged by jenkins-bot:
Add keyboard shortcuts for strikethrough and code annotations

https://gerrit.wikimedia.org/r/160174

Verified the fix in production