Responsive Menu - Accordion (with submenu toggle) to Dropdown:
Item 1 (external)
Item 1A (external)
Item 1B
Item 2
Item 2A
Item 2B
Item 2BA (external)
Item 2BB
Responsive Menu - Accordion and Drilldown both with parent links:
Item 1 (external)
Item 1A (external)
Item 1B
Item 2
Item 2A
Item 2B
Item 2BA (external)
Item 2BB