Amplify command is one of the most important ways on OpenMPT to change volume values of notes. I think that the window which opens when invoking an amplify command should also display the absolute target values (which would change according to an amplify percentage suggested by a user). If a selected piece of pattern contains several different volume values, the very highest and the very smallest value could both be displayed. Without this option users often make guesses with percentages and then use the amplify command several times in order to reach desired values. But if absolute target values would be displayed, changing volume values would be smoother.