UE4 Editor:
-Pressing backspace in the Content Browser should go up one directory.
UMG:
-You should be able to select a widget/control and use the keyboard arrow keys to shift its position X/Y values by one unit (similar to nudging an object in photoshop). Additionally, if you press Ctrl + [arrow key] it will move the selected objects by the amount listed in the snap value dropdown.
Super crazy wishes:
-The color picker lets you specify RGB values by either a complete hex value, or per color channel by a float which ranges from [0.0 -> 1.0]. It would also be awesome if we could specify per-channel RGB values by individual byte values [0-255], similar to how you can do this in MS-paint and photoshop. Even a little checkbox beneath the RGBA values to toggle between float and byte values would be good enough I mean, if you look at the RGBA value [1, 0.753, 1,1], you can’t immediately tell that 0.753f is the same as the byte value of 192.