The Apple IIc and "enhanced" IIe included custom bitmaps in their character ROMs called "MouseText". Many of the bitmaps look like they might be useful as parts of scrollbars or titlebars or whatever, but I've never been able to find any solid guidance on how they were expected to be used.
The 1985 "Apple II Human Interface Guidelines" mention "MouseText" and "MouseGraphics" UI toolkits available from Apple, and on page 96 where it describes "windows" it even has a side-by-side comparison of a generic window drawn with "MouseText" and one drawn with "MouseGraphics", but I've never found any "MouseText" library in archives of Apple's developer tools or any further information of any kind.
I can't prove it but I suspect that the Bánffy, Ricardo cited in reference 3 and 4 is the rbanffy seen here and on the orange site. maybe these are bread crumbs to help your quest. apologies if you knew these details already.
For example, the screenshot in the 1985 Apple II HIG shows something like the character at 5E (in the table on Wikipedia) being used for the close box at the upper-left... but is that intended? The character at 5E doesn't have a left-hand edge, and I'm guessing that it's supposed to be used next to the character at 5A to provide that left-hand edge, but that's just my guess. I'd like to find some more reliable source.