I don't know if I'm authorized to write one of these, but this one has proved extremely useful to me time and time again, and I haven't seen it documented. very nice time saver
in many situations where you think you'd have to copy and paste and expression or start from scratch to do something slightly different, construct's smart back button comes in handy.
Let's say you have a condition where if the x coordinate of sprite0 is greater than some complex expression, you take a certain action. Oops. Maybe you really should've tried this with sprite1 instead. You don't have to redo the whole thing with sprite1. Go into your original condition, and click back repeatedly until you can choose a different object. choose sprite1, and choose your the x coordinate condition again, and your complex expression will still be there. Did you mean to use the ycoordinate instead, click back and choose that condition. Even though it's a different condition, it will have your original expression where you'd expect it to be.
This works for much more complex situations as well. Suppose you had made a normalmapped sprite and you had the infamous lightsourcing expression "(MouseX - Sprite.X) / Sprite.Width" set for lightx. Now you realize you really wanted to use a heightmap instead. You don't need to copy and paste the lightsource expression or start from scratch. Add your heightmap effect before you delete the normal map, and then go into your normalmap:set lightx action, and hit the back button until you can choose heightmap instead of the normalmap. you'll notice that lightx is already selected for you under the new heightmap tab. press the next button repeatedly, and you'll see it's all filled out for you already.
The back button has this memorization feature in almost any situation you can think of that'd be annoying to redo, so try it out before you take the time to start an expression or condition from scratch. If you happen to stumble upon a situation where it doesn't work, you don't have to fear losing your brilliant expressions. Hit the cancel button, and everythings back to where you left it.