Mavericks' Quick Look for joining QTs; adjusting brightness; & opening folders in new window

Question

In the absence of readable guidance from Cupertino I’m still riding bareback on Mavericks, having been rash enough to install it a couple of days ago. And I apologise if any of the following thoughts has already appeared in this website.
1) For some occult reason Quick Look no longer allows me to string QuickTime movie files together for continuous play. A vandal seems to have been at work.
2) Mavericks’ infamous refusal to recognise the (extended) diNovo Keyboard Mac® Edition’s venerable F1 and F2 keyboard tricks for lowering and raising the brightness of the screen has led me to ferret out a trick that does work with the diNovo in Mavericks: fn F14 and fn F15. That trick requires only one hand. Grudging tick, VG.
3) Mavericks’ infamous refusal to recognise a simple double-left-click of the mouse as a way to open a folder in a new finder window has persuaded me to try to get into the habit of using single-right-click and then choosing the first of the options that appear in the little list, “Open in New Window”. That trick requires only one hand, and doesn’t involve the keyboard at all. All I need do is remember not to try the time-honored double-left-click method, which of course still works on my trusty PowerBook with OS 10.5.8.
  4) And I now understand why the boys and girls in Cupertino abolished the fully colored file-names or folder-names in the finder: They believed that we wanted to be able to assign more than one tag (formerly known as labels) to certain files or folders with the help of those tiny circular blobs and that we wanted to struggle to distinguish the blobs of one color from the blobs of another color.

Answer 1

Ah. In the case of Quick Look my trouble is more complicated than I describe in my earlier post. I now see that my trouble with QL in relation to QuickTime in Mavericks is that in my main user-account QL happily opens a QT file that I created in that account, and strings together two or more QT files  for continuous playing, but that in a second user-account (whose original purpose was to let me test things when I struck a glitch when using my main account) QL  refuses to play pretty well any QT file that I created in that second account, and of course refuses to string together pretty well any group of QT files.
And I find that in Mavericks when I do manage to get QL to play a QT file whose aspect-ratio I’ve already corrected permanenty in QL the ratio is (usually? I haven’t determined that yet) wrong when playing the file in QL. That problem doesn’t exist in my PowerBook with OS 10.5.8. My PB works perfectly in all matters to do with compatibility between QT and QL.
I wish I hadn’t caught Mavericks, doctor. Is there a cure?