Perhaps this has been discussed before but if you use...
On Start of layout
It does not wait.
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Well if you just use the wait action by itself alone, indeed, it does nothing. The tutorial about the wait action mentions it.
Consider this capx, the sprite becomes effectively visible after the layout has been displayed for 5 seconds.
The action of the "On start of layout" event has effectively been delayed.
I'm wondering what exactly you're trying to achieve ?
Do you want to delay the apparition of a layout between a switch from a layout to another ?
If that's the case, I'd put the wait action right before the "go to layout" action in the previous layout, not on start of the new one.