In prefs -> folders -> folder display there is an option to change file names from "uppercase" to "capitalize first letter only".
It seems, it does only work for folder names here, although the translation says "files".
It works the way it should for me. For both files and folders.
It works fine on both files and folders.
The option is called "modify display of all-uppercase files"; it only affects things whose names are entirely uppercase. At least in the past, those usually came from MS-DOS filesystems which didn't support mixed-case, so Windows/Explorer made them look prettier by displaying them in lower-case (except the first letter). (If a file isn't all-uppercase then you know its name isn't from an MS-DOS filesystem.) Opus lets you do the same thing, but it's optional.
I´m not sure, if i interprete it right. For example renaming test files to upper case remains upper case. Or files named like "USB.png" stay that way, where i would suppose
they should change to "Usb.png", as long the extension part isn´t considered to be also in caps (referring to Leo´s answer). Not sure, why it doesn´t work here on files.
Ok, explanation found: it works only on entire upper case files like EXAMPLE.EXE, while doesn´t on EXAMPLE.exe. (Leo pointed that out already, i was just doing several things in parallel & overread that).
The extension has to be in caps too.
Yes, now it´s clear, it´s because of the old DOS stuff, like sometimes in old DOS games. 