When you add many custom visualizations - you should be able to expand the width of the window and have the icons fille the Space (as currently happens) but also have the Details below scroll up into the newly emptied space. It is very difficult to see/view and edit values and filters, etc. when the space is small from many visualizations being added.
Also, The Selection Toolbar/Menu does not have a scroll bar to scroll down. Making it useless if you have a complext report build as you can not scroll down to select or unselect items.