is copy pasting sudo password from opened document a possible vulnerability?

During setup of my ubuntu systems after installing the system offline i open a textfile and change my sudo password by typing it into a textfile and paste it after so that i don't lock myself out by accident. My passwords are 20 characters long and have special character and everything. So my question is if this behaviour is a vulnerability as soon as the system goes online. Because of the password lenght i use to fail quite often when typing it in blind so i type it into a textfile and then paste it into the terminal also when i am online.

I was thinking that if someone would have gained acsess to my system it would make no difference if i type the password in by keyboard or first type it into a text document and then copy paste it please correct me if i am wrong.