Hi @mbra2
To set an LTI so that it is visible only to instructors and not students, the necessary setting is "visibility":"admins", but I'm not sure you can simply add it in the Custom Fields area, or if you need to set up the LTI by pasting XML and including the it in the Course Navigation settings part of the XML, like
<lticm:options name="course_navigation">
<lticm:property name="default">enabled</lticm:property>
<lticm:property name="text">Tool</lticm:property>
<lticm:property name="url">https://toolurl.com</lticm:property>
<lticm:property name="visibility">admins</lticm:property>
</lticm:options>