For those interested in the contents of their Payee list:
- Go to Settings→General→Early Access
- Turn on "Early Access"
- Go to Reports→Income & Expense
- Select a "Date Range" that starts before your earliest transaction and ends today
- Select "Payee" from the "Row" dropdown
- Select "Usage" from the "Column" dropdown
The resultant table should now display all your (non-zero) Payees in the left column.
I've found the list useful for identifying duplicated Payees (i.e., misspelled, uppercased, abbreviated). Once identified, one can use the transaction window to consolidate payee transactions by bulk updating the duplicate Payees to the "default" Payee (albeit with some tedium).
I'm sure there are other uses. If nothing else, it may satisfy some curiosity about the state of this secret list.