If you can write using the numeric keypad, that means you already have the code point for the character. Simply enter the hex value of the character(s) you want into notepad++, select them then open menu Plugins > Converter > HEX -> ASCII
You can also get live results from the conversion panel
Another way is using the HexEditor plugin, which was included in prior versions of Notepad++ but was removed recently. You can still install the plugin (or reactivate it if it was disabled) from the plugin manager with the caveat that sometimes it may be unstable
This way you just select Plugins > Hex-Editor > View in HEX (or click the
H button near the right of the menu bar) then type the UTF-8 bytes into the hex edit window. For example to get the string 🔙🔚🔛🔜 (I copied from above) which is
f0 9f 94 99 f0 9f 94 9a f0 9f 94 9b f0 9f 94 9c in UTF-8, just type those hex values in to dump column and switch back to normal text mode, you'll see those characters appear.