Rather than creating 30 variables or 30 properties in the app, I would create a vector that can contain 30 edit box handles and use indexing to address the appropriate edit box handle. While in the example below I'm manually creating the edit box handles in specific positions, you could automate this if you wanted.
f = uifigure;
P = f.Position;
W = P(3)/10; % 10% of the width of the uifigure
H = P(4)/10; % 10% of the height of the uifigure
obj = gobjects(2, 2);
base = [W H 3*W 3*H]; % Base position, lower-left corner
obj(1, 1) = uieditfield(f, 'Value', '(1, 1)', 'Position', base.*[1, 6, 1, 1]);
obj(1, 2) = uieditfield(f, 'Value', '(1, 2)', 'Position', base.*[6, 6, 1, 1]);
obj(2, 1) = uieditfield(f, 'Value', '(2, 1)', 'Position', base);
obj(2, 2) = uieditfield(f, 'Value', '(2, 2)', 'Position', base.*[6, 1, 1, 1]);
With this you could adjust the properties of the edit fields using the elements of obj.
obj(1, 2).BackgroundColor = 'r';
