Specifying File Variables

https://www.gnu.org/software/emacs/manual/html_node/emacs/Specifying-File-Variables.html#Specifying-File-Variables

You can use M-x add-file-local-variable-prop-line instead of adding entries by hand. This command prompts for a variable and value, and adds them to the first line in the appropriate way. M-x delete-file-local-variable-prop-line prompts for a variable, and deletes its entry from the line.