Using your client for years and its great compared to other options, but this single thing is getting on my nerves for so long. Im actively using all my e-mail folders and this submersion is (for me at least) very user unfriendly.
I have tried several times past few years to find a setting where I could turn it off without success.
The More folder is a place to hide other folders you do not ordinarily want to see. That is why it is collapsed on start.
To move a folder out of More, expand it, then right-click on one of the folders and choose Show. Once all the folders are removed, the More folder will disappear.