You can enter characters using hexadecimal Unicode code points.
In the CotEditor app
on your Mac, open a document.
Move the insertion point to the location where you want to enter the character.
Choose Edit > Insert by Unicode Code Point.
Enter a code point in the field, or choose one from the history.
Press the Return key.
You can enter either a plain hexadecimal code point or one prefixed with “U+”, “0x”, or “\u”. For example, “1F603”, “U+1F603”, “0x1F603”, and “\u1F603” all insert “😃”.