Extensions Settings
If you enabled one or more extensions in the global settings, you can change their configuration in two places, depending on the integration: in the global extension settings or in the project settings.
For example the Integration for Slack is global and is configured directly in the Extension settings where the plugins are enabled. The Jira or GitLab integrations on the other hand are per project and can be configured in the Extension settings of each project (same for the Link Plugin extension).