I thought the right pane was just for adding words so you can abbreviate them on the left side. For example, when I put {PARTICIPANTS} in the left pane, the email will read Participant(s) because that is what is what I added in the right pane. I was just hoping I could add the list of participants to the corresponding cancellation email so I didn't have to go back into the system and search for the deleted conference to find the names.

Yeah, you're correct.  Either way, variables can't be taken from one template and put into another, the admin guide lists following variable that can be used with the booking cancel template:

<SECTION:MEETING_TITLE> // Used if conference has a title.
<VAL:MEETING_TITLE> // The conference title.
<SECTION:RECURRENCE_INFO> // Used if conference is recurrent.
<VAL:RECURRENCE_INFO> // The recurrence pattern information.
<VAL:MEETING_DATE_TIME> // The conference date and time.
<VAL:MEETING_TIME_ZONE> // The conference time zone.
<VAL:OWNEREMAILADDRESS> // The conference owner email address
<VAL:OWNERPHONENUMBER> // The conference owner phone number
<VAL:OWNER> // The conference owner.
<VAL:DELETED_BY_EMAILADDRESS> // Email address of the user who deleted the conference
<VAL:DELETED_BY_PHONENUMBER> // Phone number of the user who deleted the conference