Essay pages are typically, but not necessarily, created under Essays, e.g. Essays/Fibonacci Sums.
To add a new Essay page, first create the page and then add it to the Essays Directory. Each entry is a normal wiki url in the form [:page:title]. The entries are in alphabetical order of page name.
A page may be given more than once, with different titles, for example:
[[Essays/Power Set|Power Set]] [[Essays/Primality Tests|Primality Tests]]
The page may include an anchor reference, as in:
[[Doc/A Source Book in APL#origins|"APL" Origins]]
A batch task run every few minutes updates the main Essays page.