Hi.
I couldn't find anything about it, neither in the forums nor in the AGS help files.
In my game a cutscene starts when looking at a certain inventory item, and after it has finished the inventory window pops open again what doesn't look very good.
I know that InventoryScreen(); brings up the default inventory window, but is there any script function existing to close it again?
No, because once the Inventory GUI pops up, it basically takes over. You will have to close it using the built-in OK button on it.
I could be wrong on this however.