As edits are made using experimental features (or not, if they're in a control group) by editors enrolled into A/B tests (see T208438), we'll want to track those edits.
Instead of tagging edits – which requires patching MW extensions and waiting for their deployment and which are then seen by everyone – it's probably better to use EventLogging and send info as events.
Here's how the EL schema can possibly look like:
|user_id||numeric user ID, unique per-wiki but not globally|
|user_name||username, unique globally|
|test||name of the A/B test (e.g. team name + feature name|
|group||which group the user is in, e.g. "control" or "treatment"/"intervention"|
|revision_id||ID of the edit|