create dropdown lists on titlebar?

Ive been trying to search this forum for making dropdown menus on the titlebar for parent/child pages. kind of like the menus are on this page https://club.aopen.com.tw/forum/ViewMemberPost.asp?MessageID=63734

im using the karma v2 theme that can be found here https://themes.wordpress.net/?view_type=slideshow&item_type=search&page_number=1&count_per_page=12&item_filter=karma

i dont know where to start…any help would be appreciated.

Thx