Create same menu type as Appearance – Themes

Within a page I have created an A – Z table, from this table I would like to click on the (eg) A, which will take me to a dropdown menu that looks the same as the WP Appearance – Themes (it shows Manage Themes and Install Themes).
I will have around 10 links within the letter A, so that when someone clicks on A it will show a link or tab with the 10 words, (not a whole page),then when hovering someone can click on any of the 10 words which will open a new page.
What I am trying to avoid is a 3 tier menu.
I suppose it could be called a cascading tab or something similar.
Many thanks