When you try to connect GitLab to Trelica you will be asked for a SCIM API endpoint URL and SCIM token. This article shows you where to find these credentials in GitLab.
Login to GitLab and navigate to Settings > SAML SSO.
Scroll down to the SCIM Token section where you can find both the SCIM API endpoint URL and SCIM token to copy and paste into Trelica.
Note if you've already created a SCIM token, you will need to find an existing copy of it, likely from your IdP where SCIM has been configured. Otherwise you will need to reset it, which will impact any existing SSO setup.