Is this what you are looking for- or perhaps you mean to increase the max capacity which doesn't seem possible within the confines of the panel.
One idea this does give me is perhaps to add increment percentages along the bottom if the bar i.e
[-90_-80_-70_-60_-50_-40_-50_-30_-20_-10_0 (normal) 110_120_130....
Naturally there's limited size to work with within the menu- so it may have to be in 20% increments.
Due to my disability, I've always a hard time adjust/fine tuning the size slider, Would be great to have the option to click 'picture size' to open a dialog and being able to type a #x# scale or zoom percentage- and possibly have + and - buttons to adjust/fine-tune- either on the drop down menu, in a dialog or both- the bigger the better!