I was literally just on the phone to our Google Adwords guy!
IMHO, the easiest way to implement what you're asking for is to set a Redirect URL as your success state for each form, rather than the standard Success or Error Message div element.
Why? Well, that way you can set page visits to said Success pages as goals in Google Analytics.
But make sure to add
<meta name="robots" content="noindex"> to these pages, otherwise you'll get all sorts of non-form traffic and that'll mess up your data.
Below is an example of how to do this — /success.
(Ignore the URL in the Action field, and set Method to GET)
You CAN get super fancy and add Link Attributes to buttons and links, but that takes time and it's much more fiddly in both Webflow and GA and probably too out there for what you need at the moment, I assume.
Hopefully that helps!