To do more detailed edits to your widgets, you can enable Advanced Mode. To do this, you will need to open your Overlay Editor's settings.

Look for the gear icon at the upper-left.

From the Settings window, go to the Editor tab, and then click the purple button that says: Go Advanced.

Take note that once Advanced Mode enabled, there's no way to return it back to Basic Mode

This mode opens up additional properties and functions for your widgets. This includes moving one widget inside another widget.

For example, this Image has been made a part of an existing Follower Alert.