If it helps, the Windows/Linux logic is basically:

• Ctrl key for triggering actions within an application.
• Alt key for navigating the UI of an application via the keyboard.
• Meta/Super/Windows key for triggering actions outside of applications (on the OS level).

Well, and Ctrl, Alt, Shift also serve for alternative characters when you’re typing. And some application or OS shortcuts wildly combine modifiers for more complex keybindings. And of course, some applications just didn’t get the note of how this generally works. I won’t claim, it really follows rules, but yeah, it’s not generally complete chaos either.

I use Toshy https://github.com/RedBearAK/toshy

There’s some small issues with the alt key behaviour in some applications (and workarounds for that), but other than that it works really well for my OS X configured brain.

There are several readily available key modifiers in Linux: Meta, Super and ISO-Level3-Shift. You can map them to keys and use them for various purposes.

What I do is map Meta to the left Windows key, Super to the right Windows key, and ISO-Level3-Shift to AltGr (that one might already be default). You can then use Super and Meta as modifiers to trigger all kinds of actions, like Super+T to open a terminal, Super+F to toggle fullscreen mode for current window, Super+Space to toggle music playback etc.

ISO-Level3-Shift will create diacritics when combined with normal keys, provided you choose the correct keyboard layout. This is useful for being able to type correctly in languages that use diacritics, but to also allow you to use a generic US keyboard so you can do programming for example.

To make these mappings you have to edit or create a file called .Xmodmap in your home dir. To bind a keycode to a physical key you say something like keycode 134 = Super_R, where 134 is a physical key code that you get from the tool xev and Super_R is the code for what you want it to do. Also, to make Super_R a modifier you have to say clear Mod4 and add Mod4 = Super_R. Most desktop environment will import .Xmodmap automatically on startup but if they don’t you can run xmodmap ~/.Xmodmap.

Once you got Super acting like a modifier and bind it to the key you want your desktop environment settings will probably let you define custom shortcuts for anything you want. Please note that there’s usually two different places for such shortcuts, one for generic shortcuts (for launching apps), usually in the keyboard section of preferences, and one where you can tie shortcuts to window functions (like minimize/maximize), usually found in the window section of preferences. Also in the window preferences you can do some cool stuff like use one of these modifiers to drag or resize windows.

Also see if your keyboard preferences let you pick a “compose key”. The Pause key is usually used for this, because it’s not useful for anything else on a graphical desktop. The compose key lets you create diacritics in an “intuitive” way, by combining two keys. If you press Pause then o then o you get °. Pause then 1 then 2 gives you ½. Pause then a then " gives you ä. You get the idea.

Yes, it is definitely possible. How it is achieved largely depends on the desktop environment pr window manager you use.

I use the meta key largely for things related to windows and workspaces. I use the capslock key as the compose key. And, the right alt key for alternative characters. Additionally, there is Ibus for typing a variety of scripts and languages.

If I remember correctly, you can define the modifier key in KDE. Not sure though, you might have to test it out.

That would be the fastest way. Apart from that, it’s very much possible by binding every possible action to different keypresses. That would be long and stenuous.