In order to ease the discovery of article and other page contents (like, wikiprojects), I propose an option for the Table Of Contents. The option would allow to display the TOC embed in a column inside the content space (on the left or the right side). The look and behavior of this column would be a bit like what you can see on the Wikipedia app for iPad or [[ https://www.wikiwand.com/fr/Liste_des_municipalités_du_Yukon | Wikiwand ]], except for the numbering. The column may be hiddable/colapsable.
The skin (Vector, Monobook,...) outside the main content space wouldn't be affected by this option.
Here are some screenshots I took from the Wikipedia app on iPad (you can find them with titles and descriptions in [[ https://commons.wikimedia.org/wiki/Category:Wikipedia_App | this category ]] on Commons):
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