How do I add an external tool to the Rich Content Editor toolbar in an account?
As an admin, you can select up to two external tools to display in the toolbar of the Rich Content Editor for all users in your account. Selected tool icons will display next to the Apps icon.
Note: Adding an external tool to the Rich Content Editor toolbar is an account permission. If you cannot add external tools to the Rich Content Editor, your institution has restricted this feature.
Add Tool to RCE Toolbar

Find the external tool you want to add [1] and click its associated toggle [2]. The toggle will only display for external tools that support placement in the Rich Content Editor.
The Rich Content Editor only supports up to two external tool icons in the toolbar. If two tools have been selected, all other toggles will lock and cannot be enabled [3].