Don't know how it compares feature-wise to Karabiner/Goku, but on Windows, you can use AutoHotkey[0] to do all kinds of global input remapping, macros, etc. Someone even wrote a clone of DWM (tiling window manager) in AutoHotkey![1].
Personally, I use it mostly to remap CTRL to Caps Lock, but once I wrote a global GUI popup for inserting reaction emojis into conversations on my work machine. AHK is really easy to work with.
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