I've noticed that many series title are not in English, I'm not sure if that's ok in the community guidelines or should I make a request to have it changed (for dozen or so on my lists).

if it isn't, I would like to see in the "My Lists" section a way to cycle through the Name and Associated names of title to the one that will be more convenient to the user/member.

If you add a series to a list manually, it will show up as the title that you entered

A just ruler amongst tyrants

I need more details on that please.

Because after you add a series to a list so far the only thing I can see that you can change/modify are the current chapter, rating, deleting from list and moving from list.

And is there a naming convention for series tile. A part from adding the Author name for different series of the same name (pointing me to a thread or post is fine too. )

When viewing your lists (https://www.mangaupdates.com/mylist.html), use the Add Series button at the top which allows you to enter whatever name you want

There's a bunch of rules for series titles, but there's no thread detailing them that I can link to you

A just ruler amongst tyrants