Just so long as we can redefine to play with legacy settings if we want to. :)

I was always missing quick-marking feature. Lets take skill list as an example. Pressing [a] shows skill list. Choosing a letter applies it. In rare cases I have to press one more key (two more key at laptop) to show next page but skill and spell list aren't that large for most builds with a few exceptions.
When you have skill quick marked first of all you can't see a list. So you have to remember what have you marked with which key right away. Secondly you can't choose non-quick-marked skill right away, you need one more keypress probably with shift on laptop (can't remember the key and can't check right now). It makes applying non-quick marked skills actually harder. Applying quick-marked skills is harder for me two since I don't see a list.

Could anyone who uses quick-marks advise... What's the point?
I'm for changing quick-mark system completely because I wasn't able to find it convinient. And I don't how this change makes it better.

This was my request so let me elaborate the use case...

The #1 problem with NOT using quickmarking is that the spell list is ordered alphabetically, so the letter of the spell you want to press is shifted every time you learn a new spell. If you are a patient player this is fine, but it is slow to confirm you're pressing the correct spell every time. While it's true you may not hit 2 pages of spells with most classes, on Wizard, Priest, and Elementalist you most certainly will - all spells in the game are 3 pages I think? You are correct that it's wiser to either completely use quickmark, or not use it at all. If you're not using at least 6 hotkeys, it's arguably not worth it.

I use the same 10 quickmarks every game, every class. This makes memorization easy. My bolt spells go on 2,4,6,8 (2 is always frost, ...), teleport goes on 9, knock goes on 7, SoA goes on 3, burning hands on 1, magic missile on 0. My ball spell-of-choice goes on 5, which is one of the biggest issues with the 0-9 limit as I don't have room to quickmark all 4 ball spells, so I have to change it depending on my situation. Anyway, my 10 keys set up, I have all my offensive and regularly-used utility spells quickmarked. Most other spells I don't cast except in special circumstances, and they're often not repeatedly cast.

What this change will let me do is generate a better pattern-based spell system, ie I can bind my bolts to z,x,c,v and balls to a,s,d,f. I can have a bind for light, dark, remove curse, identify. I no longer have to choose whether 7 should be knock or heal.

I see your point but I really would love to see a solution which would allow to use quick marks without two drawbacks I pointed out.
When I was starting playing ADOM I had no idea which spells would be useful and which won't. And I wasn't able to memorize them.

1st: show skill / spell screen if quick marks are set.
2nd: allow to chose a non-quick-marked skill / spell from the same screen pressing [a] - [t].

Your suggestion makes sense but it wouldn't let [a] - [t] to be used to trigger non-quick-marked skills / spells meaning that solution without additional keypress will be impossible.

What if you couldn't quickmark with 'a' but only with 'A'?

I like it. But it would decrease value of quick-marking because [A] requires [Shift]. @harpo, your view? You're request owner :)

Adds unnecessary tedium and is extremely prone to mistakes. Not a fan.

Then how would you suggest the interface someone who has a mix of quickmarked/non-quickmarked spells? If [a]-[z] are taken, what should they hit?

This is really only a problem per ixi's suggestion, not with the current UI (you still access non-quickmarked spells with * first). It's not a bad idea to think about, but my request is much simpler. This doesn't change anything with the current UI as you currently can't press a-zA-Z when in the quick-cast prompt, so it's just unlocking more options, not changing anything.

Simpler to implement - is not an argument. User experience should take preference.
(Unless I'm asking to build holographic image with skills controllable by mind-reading device to trigger them. Hope I'm not.)

But I do agree A and a isn't a good idea.

Whelp, upvoted.

If quick marks are used skill can be used with [A] with only [Shift] additional keypress which looks fine. Spells require [:Z] which is worse but one can redefine this key. If separate commands to apply skills and cast spell will be preserved with this change I'm for it.