Heyall.
I was wondering how many custom panel can you have in Quest? Can I make more custom panels in addition to the normal 5? (Inventory, places, Compass, Commands, Custom panel), and can I change their alignment from left to right?

Overall are there forums specific for HTML/CSS/JS for Quest? I'm eager to learn more aspect of the GUI. (I've already read the tutorial/articles on this site.)

You get one custom pane by default. It's relatively easy to turn the Status attributes pane into a second custom pane if you want to do that (if you have a single status attribute whose contents is a whole bunch of HTML, it will be sent to the status attributes pane exactly as it is).

Beyond that, you would need to put something in the UI initialisation script to make a new status pane, and then write your own javascript functions to update it. I think there's been people posting here how to do that in the past; but it's more complicated than it should be, with some hidden gotchas.

I have little to moderate knowledge about HTML/CSS/JS, but the problem is how they're used/translated in Quest which I have no idea. (It doesn't help that I don't know much about JQuery.) There isn't many tutorials on this subject too. btw, what's the Quest's language? Is it Java?

Is the QuestKit section of the forums more appropriate for JS questions?

Pixie has a library and instructions on how to set up an additional "inventory pane" here. I've used it for two additional panes by changing the 2s to 3s, etc.

https://github.com/ThePix/quest/wiki/Library:-Second-inventory

Works great for adding something like a Spells pane, or a book-reading/journal pane.