Quotations from the changelog:
Bug 40059: YEC activist sign empty in
about:toron RTL locales
Bug 40383: Workaround issue in https-e wasm
I assume this has something to do with Tor Browser localization in languages that are read and written from right to left and "...-e" could stand for "experimental" or "enhanced".
Wikipedia has no clue and Tor Browser User Manual is lacking a Search feature.