Construct already loads layouts in to memory when you switch to them. The only reason to use it is to pre-load another layout before you switch to it, making it faster to load the layout. Typically this is done on a separate loading screen. Loading another layout's images while still on a gameplay layout is dangerous, because it will temporarily spike the memory use, and risk crashing the game as it runs out of memory.
If you want to reduce memory usage, you will need to remove objects or unload memory - not load even more things.