Account linking and access help across Coda, Grammarly, Superhuman Docs, and Go

Unfortunately, it’s unusable for me because 1) I have an old email (via Google Sign on) hooked up to Grammarly, 2) my new email hooked up to Superhuman Go, Email, and Docs and 3) no way to de-register or transfer my paid grammarly account to my new email and, since my new email is registered - I cannot do the normal email transfer because I get a “this account already exists” error. The rollout of this “integrated platform” has been totally dis-integrating. I have been a dedicated user of all three platforms prior to the merge, so I find this super frustrating.