Can't get stackeditDOTio to synch with GitLab

I’ve tried using this GitLab Help page to enable to connect with a GitLab repository I created for the purpose:

I’ve tried different URIs and so on and all I get is:

An error has occurred
The requested scope is invalid, unknown, or malformed.

Q: Is the URI I submit to stackeditDOTio my base GitLab URL ( or do I need to supplement that URL with /users/auth/gitlab/callback as seems to be suggested by the GitLab online help page?

2020- 04- 28_ 0824 StackEdit

Q: Is the callback URL I specify when creating the stackeditDOTio application the one given in the stackeditDOTio Link Your Application dialog shown above

The online page also refers to Admin Mode. I’m unable to access that – among other things I don’t get the wrench / tool icon shown in the OLH page’s screenshots.

Thanks in advance,