Once the character encoding menu used to look like this: https://www.youtube.com/watch?v=vUdrVRsn5L8
The original character encoding menu was much more functional than the current one. It even had the possibility to add and remove encodings. Then it was replaced with the current menu by Mozilla developer Henri Sivonen in 2014. Since then Mozilla browsers have not been able to display many pages correctly. Especially viewing text files in the browser is problematic. I often browse pages and sites that are at least partially written in IBM850 encoding.
The original encoding menu was/is better in every way possible and I'm sure many users would benefit from it if Seamonkey switched back to the original menu.