@biberI am not the one you need to convince. It‘s your data and you can do with your database whatever you like. I was just puzzled by what you want to achieve or whats your problem is or if there is any at all. All still not very clear to me to be honest. What caught my attention was that I got the impression that you wanted to alter the text representation in the database, as the database values don‘t show up UTF8 chars but store German Umlauts in an encoded representation. Thats where my advice came from, not to alter or manipulate DB charset/collation manually, if text shows up correct in the frontend. Doing so will most likely corrupt your database and you need to go deep inside the rabbit hole to get charset/collation and data right.
Of course you can modify, copy, rename or delete fields with PHPMyAdmin or from the Adminer module from the backend. Adminer is part of the Tracy Debugger module for example.
However, for me it‘s just not clear, what you try to do and why it‘s necessary to do. If it‘s just for experiment, than I would just go with phpMyAdmin or Adminer and change some content and see what happens.
By the way. I write most of my websites with plain HTML5, CSS3 and vanilla Javascript/Typescript and or PHP 8. Just for projects with multiple users or changing content, I prefer Processwire CMS/CMF which saves me a lot of work. However in those cases I rely on the PW core and API and only modify/dig deeper into the core or database if there is a real need for me to do so.