Based on the knowledge sources provided, I don't have specific information about what happens to dashboards when you delete a formula from Lexicon. The documents mention that Lexicon contains metadata about various Mixpanel UI elements including formulas, and that you can manage existing formulas through Lexicon, but they don't explicitly state the impact of deleting a formula on dashboards that reference it.
For comparison, we can see that when editing a saved behavior, there's an option to "Save for Everyone" which "will update the definition of the behavior for yourself, as well as in any report that is using the saved behavior" Saved Behaviors. This suggests that Mixpanel generally maintains relationships between saved elements and the reports that use them, but I don't have explicit confirmation about formulas specifically.
To get a definitive answer about what happens to dashboards when deleting a formula from Lexicon, I would recommend reaching out to Mixpanel support for clarification.
