Support for timing. If a button, as an example, should not appear until the end of a video - there's no way to use a property/setting to change the timing for when the button should appear. Currently, the only way is to drag the beginning of the button manually on the timeline - and that is "buggy" if you have to drag beyond the time visible in the timeline. The timing properties should include Appear After (for when the item should start to appear) and the length of appearance (at least second-based; and for rest of slide values)