Remap modifiers keys to press multiple modifiers at once - keyboard

Question

I would like to remap a modifier key, in my case CAPS_LOCK, to send multiple modifiers at once on its one. By that, I mean not a specific combination of keys, like <Ctrl>+C. While the second part, mapping a key to a key combination, is answered in multiple questions, I have not found a solution for the first problem.
https://unix.stackexchange.com/questions/11182/mapping-key-combination-with-xmodmap shows how to map to a specific key combinations
https://wiki.archlinux.org/index.php/xmodmap#Reassigning_modifiers_to_keys_on_your_keyboard Xmodmap, while able to create multiple layers for your keyboard, does not support this
https://ubuntuforums.org/showthread.php?t=1764318 I have seen AutoKey mentioned a few times, but you cannot map to a modifier key
https://unix.stackexchange.com/questions/11182/mapping-key-combination-with-xmodmap The proposed combination of xbindkeys and xmacro also does not seem to support this
https://www.semicomplete.com/projects/xdotool/ Xdotool seems promising, but the documentation is quite lacking
To make things more specific: I would like to remap Caps_lock to Meta+Control+Alt+Shift so I have a modifier key that does not conflict with any other key combinations defined by system applications. The combination is a result of sharing my PyCharm and Intellij keymap between a Mac and my Ubuntu machine and on Mac I use Karabiner to map the caps lock to a so called Hyper key, which is the combination of the above mentioned modifiers.

Answer 1

I realize this thread is old but for others like me who stumble by, this is how I've successfully mapped the caps lock key on my Apple Magic Keyboard to left-command+left-option+left-shift:
{
"manipulators": [
{
"description": "Change caps_lock to command+option+shift.",
"from": {
"key_code": "caps_lock",
"modifiers": {
"optional": [
"any"
]
}
},
"to": [
{
"key_code": "left_shift",
"modifiers": [
"left_command",
"left_alt"
]
}
],
"type": "basic"
}
]
}

Answer 2

[To prevent misunderstandings: do you mean "at once on its OWN"? You typed: "on its ONE"]
As its name insinuates, caps_lock LOCKS its state permanently (on my Windows keyboard).
MEANING: pressing caps_lock once returns "eventType: key_down" (in K-E's EventViewer) and only a second press will invoke "eventType: key_up".
So if you plan to "send" and be done with it, I'm afraid caps_lock prevents this "mechanically".
(This is confirmed/illustrated by: if you code an additional "to_if_held_down" with a long waiting time -2s- and press caps_lock shortly, your "held_down"-commands will STILL be executed after 2s.)
SO: if your Apple/internal keyboard behaves DIFFERENTLY: please comment HERE !!!
I am not sure that I got the "intention" of your question (see comments) but I'll still try to answer.
The current version 12.1 necessitates manual editing of your ~/.config/karabiner/ karabiner.json file for complex remaps (until a final "non-elements" version is released).
Following code works very well for me in principle, but its state is toggled key_down/_up:
{ "description": "META-Cmd & Shift & Control & Option",
"manipulators": [
{ "from": {
"key_code": "caps_lock",
"modifiers": {
"optional": [ "any" ] }
},
"to": [{
"key_code": "left_command",
"modifiers": [
"left_shift",
"left_control",
"left_option" ]
}],
"type": "basic"
} ]},
My Windows keyboard toggles EVERY time I press it, no matter what my settings in Sys-Prefs Keyboard Special-Keys are. (I read somewhere that a Microsoft driver may be the cause.)