Lots of good ideas, but I would suggest starting with very simple strategies to just raise visibility. Even a well-targeted banner with a clean (multilingual :-) landing page would go a long way. Why not start there and see what it does to your # of testers?

@Eloquence, I agree in starting simple, but I would prefer to ask the user in a relevant context (with some chances to be interested in translating).

I created a prototype for one of the ideas: tell the feature exists when the user is about to create a new page. Clicking on "Try Content translation" would enable the feature and direct the user to CX to start a new translation.

Here is a gif file with the animated globe:

Change 191322 had a related patch set uploaded (by Santhosh):
Campaign: Invite editors to try while creating a new article

https://gerrit.wikimedia.org/r/191322

Patch-For-Review

Screenshot after implementation

Change 191322 merged by jenkins-bot:
Campaign: Invite editors to try CX while creating a new article

https://gerrit.wikimedia.org/r/191322

Change 194453 had a related patch set uploaded (by Santhosh):
Campaign: Set max width for the invitation dialog

https://gerrit.wikimedia.org/r/194453

Change 194453 merged by Nikerabbit:
Campaign: Set max width for the invitation dialog

https://gerrit.wikimedia.org/r/194453

Scheduled for Catalan Wikipedia today (3/19).

Deployment was reverted, moved to next week in roadmap.

Postponing deployment further due to fix for T92232 not being merged and deployed yet.