This is a sample configuration for Karabiner Elements that allows to define keyboard shortcuts for typing Unicode characters in MacOS. I've seen other solutions using bash scripts but this one leverages a different route: it simulates temporary switching the input source to the "Unicode Hex Input" and typing the Unicode character hex code while the Option key is pressed. For this to work, the Unicode Hex input source must be enabled in settings.

I can't make it work, even though I installed the Unicode Hex Input in my list of sources. I'm getting a series of 4 characters when I press the defined key, instead of the output character. Example: your first shortcut to produce the right arrow.

Perhaps it's the fact that my right option is remapped to right command (but my right command is also remapped to right option)?

To be frank, the solution above also tends to work for me only in some applications but not in others, and in yet others it behaves randomly… I was not able to find the root cause for that yet. In my case, when it fails, it also prints a series of weird characters. I guess it's some kind of timing issue but who knows, sorry.