make the window size resizable

There is a "presets" function in the "tools" menu which does just that. Lets you save any time settings you wish, then allows you to recall them easily with just a click from the menu. Just set a time on the timer, click the tools button (gear on the toolbar) then click "Save currently set time as preset". That time is then saved in the presets menu available for use when you want to automatically set the timer for that time.