Bubble App Connector - Login from multiple pages

I’ve successfully set up Bubble App Connector using Neeja’s excellent post:
http://forum.bubble.io/t/how-to-make-sub-apps-use-the-main-app-credentials-for-login-signup/20161/4

I have my main app “App A”, and a secondary app, “App B”.

I would like to put the login link in the header of “App B” so it appears on every page. In “App A” I have to put in a Redirect_uri but this would only apply to one page in “App B”.

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Is there a generic Redirect_uri I can use? Is there another way to set this up so that I can have a login link on every page in “App B”?