Mainly organization and bringing it closer to the Add menu in the 3D Viewport. * Icons for most top-level items when available. * New Transitions menu for Cross, Gamma Cross and Wipe. * Move Color and Text to top level. These options are used way too often to be in a submenu. Having a menu with 2 entries defeats the purpose, so I've removed it for now. I checked if add-ons used it and apparently not. It can be brought back if needed. * Avoid empty dropdown in Scene/Mask/Clip. Solution is ugly for now and should be improved in C. * Some effects couldn't be used without 1 or 2 strips selected, now the menu entry is grayed out accordingly. * Some more icons for other menus.