Cherry pick multiple Collections under different Main Menu link

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I have parts for a Bronco and Mustang. My collections have names with those names in them. My homepage has Main Menu items/links for Mustang Parts and Bronco Parts. Currently when selecting which collections I can add to those Main Menu items it only gives me the option to add one collection or all collections. 
I only want to add Mustang Collections under the Mustang Parts Main Menu item, and Bronco Collections under the Bronco Parts Main Menu item. Would be nice if I could checkbox or something only the collection that I want under each Main Menu item. Whats the solution?