How to place community spaces in other worlds?

It does save them all separately to the gallery. So, if you are currently in the mode to build the garden and then save it, it will save it as a community garden. If you want to import and export all 4 modes, you will have to activate in build mode and save all 4. You can also import a community space, go into build mode and change the other 3 or download a different version if you wish as long as the tags match (eg, replace a garden space with a garden space).