I would like to map the "Link to Issue" mappable to the dedicated Jira Issue field provided by Asana's Jira Cloud Add-on rather than, just mapping the "Link to Issue" to the "description footer" mappable.

The Field name is "Jira Cloud", it is not a mappable option. It is a field added by an add-on but, the add-on is made by Asana so, I request that you support it. It allows you to paste a link pointing to a Jira Issue from which, a pretty card is displayed within the details panel of the Asana task showing jira-issue details like status, priority and assignee.