Complete List Of [[variables]]

Is there somewhere I can see a complete list of the [[variables]] defined in payplans? The user custom details documentation link on my admin side just circles me back to the edit custom details page.

Also, when I create a custom detail parameter under orders->custom details, does the name of the parameter become a variable automatically?

For example, if I define...

<config>

    <fields name="subscriptionparams">

        <fieldset name="subscriptionparams">

            <field name="PREFERRED_DELIV" type="list" label="Preferred Delivery Day">

                <option value="sunday"> Sunday </option>

                <option value="monday"> Monday </option>

            </field>

        </fieldset>

    </fields>

</config>

Will [[PREFERRED_DELIV]] become a variable?

Thanks!

EDITED:

• Clarified that I was looking for variables.
  
• Tried all caps with underline as field name.