I want to have a login nugget/module on all pages at the top right corner.
Any ideas how to work around this? Can login pages etc be included with SSI instead?
What was the problem you encountered adding the login to the template.
You can add the form for the username and the password to the template, then add the Security Assist Authenticate User Server behavior.
To be able to add that as a server side include, you would need to create on SSI with the Authenticate user server behavior in it and another with the form in it. The SSI with the server behavior would need to be added at the top of the page, before the doctype tag.