The deployment of T239676 will introduce an option for all contributors, including those included in our ongoing A/B test , to opt into the mobile wikitext editor, even in instances when the mobile visualeditor would have otherwise loaded by default. 
To ensure these contributors are appropriately accounted for in our analysis, we will need to add new tracking events that enable us to see which users assigned to the `default-visual` bucket have opted into the mobile wikitext editor by way of the new "fallback workflow" T239676 will introduce.
- [ ] Instrumentation is added to track contributors who engage with the "mobile wikitext fallback" workflow such that we can segment them in our analysis (T221198)
2. E.g. a contributor in the A/B test could be assigned to the `default-visual` bucket, but elect to use the mobile wikitext editor if they felt the mobile visual editor was taking too long to load.