Is it possible to cut a method function from the .mlapp file into a separate .m file by creating a library of functions?

For example:

    function summ(app,a,b)
        app.EditField.Value = a + b;
    end

[qwer ty]

Scare class size. And the fact that you can not make a dark theme and increase the text volume in App Designer. Then very tired eye.

[qwer ty]

Ofc i can do that

% IN .mlapp file
app.EditField.Value = summ(a,b);

% IN .m file 
function c = summ(a,b)
    c = a + b;
end

But i need use eval include app. dot prefics.