I imagine some of this stuff just hasn't been implemented yet (as it's already in Construct Classic) but I thought I'd post it anyway.
-The ability to tab through object properties and such. I prefer using the numpad on the right side of the keyboard here, so I constantly have to alternate between that and the mouse.
-The ability to collapse sub-events
-"Auto-finish/correct" expressions. If you type something like player.x and press enter, it will be changed to player.X first. You have to press enter again to close the window. I know, it's not a big deal, but it is kind of annoying sometimes when I'm working quickly! It would be cool if the expression is just 'corrected' automatically, like in this case, as soon as I type in x.
-More hotkeys for the event sheet editor. Maybe s for a new sub-event, t for toggle, e for new event, c for comment? This one's kind of pushing it, but what about - or + plus hotkey to make a new event/condition/action above or below the currently selected one?
-Hold left mouse click + use mouse wheel (or arrow key) to move a condition, action, or event up or down a slot.
-Copy & Paste frames in the image editor.
-More of a bug I think..Dragging an event under a different event that has sub-events doesn't work.
Hm I thought I had more than this..might add to it later!