@molly_fatearth apologies for not being clear in my initial response. To clarify, to my knowledge, there is no way to find out which Gmail users have marked your emails as spam.
Which is why sending to engaged segments and sunsetting disengaged email subscribers when appropriate are often the best approaches we can take to mitigate sending to those Gmail recipients that have previously marked an email as spam.
Would be curious to hear from others in the community though if what I shared above sounds accurate. Or, if anyone knows of a way to have visibility into the individual Gmail recipients who have marked an email as spam, please reply!
Cheers,
Bobby
Freelance Klaviyo Marketer | Klaviyo Partner & Community Champion | check out my services: bobbyleonard.me