Okay, I deleted statements X Is on screen at platform and coin delete event, cause they are not needed(if the other condition is true, X is on screen has to be true so it doesn't matter).
First lets fix the bug where coins appear after a while when the game starts so we actually can see them spawn.
So what I'll do, is to create On start of layout + for each platform event and copy the create coin action.
So this one is fixed, ok.
Now, the problem you asked for, when we move up, we can see spawning the coins on newly created platforms. There are 2 problems with it. We spawn coins every 3 seconds, so if a platform spawns at time 0, a coin will appear after 3 seconds have passed, so delete this condition. Ok it seems to solve the problem, but I've mentioned 2 problems right? The other one is this:
Your code spawns the red platforms, so they are spawned at the top of the window and move down, but not above it like the blue platforms. To solve the problem you could move the creation point up a little bit so you can be sure the coins will always spawn on them outside the visible area : ).
Sorry for the long reply but I didnt got a notification that you replied.