This would improve the gui workflow by a lot, I sincerely hope this makes the backlog! Especially since the lack of “size” handle makes you resort to modifying all values by number fields right now. Clamp and snapping would also be a huge boost in productivity.
Regarding snapping, you can hold down the shift-key while dragging the move-manipulator. This makes it snap to the grid. The grid is “auto” by default, but can be configured differently in Preferences under Defold > Scene Editor. Was this what you were asking for?
Yes more or less, hidden hotkeys Great to avoid decimal values! But an even better albeit very advanced version would be if it “snapped” to other elements as well, showing you guide-lines according to other gui-nodes. Indicating pixel distance and other useful information. A good example of this is the Xcode layout editor.
Now this image only display how it relates to “center” alignment within a view, but it does the same when you drag elements close to other views. Think the basic rule-set is that it displays center and edges, with an added padding as can be seen in image where close to borders of the view.