Alvin,
I’ve spent much of the last week trying to make sense of this.
As Dan says, the default location is:
~/Library/Containers/com.realmacsoftware.rapidweaver/Data/Library/Application Support/RapidWeaver
But I found beyond any reasonable doubt that RW 7(.0.2) does move Addons (which would probably include the Stacks that you’re having to chase); and create other directories to hold them than:
~/Library/Containers/com.realmacsoftware.rapidweaver/Data/Library/Application Support/RapidWeaver
I did, I think, though, find two ways to stop this happening; at least the first is logical and predictable:
1 - tell RW where its Addons should be by manually moving them - e.g. into DropBox so that they can be shared between machines
2 - uninstalling older versions of RW6 and 7 completely… they may confuse the active installation
Then thre is a line in this file:
~/Library/Containers/com.realmacsoftware.rapidweaver/Data/Library/Application Support/RapidWeaver 7/ RapidWeaver 7.log
indicating where RW where should look for Themes - presumably including, I hope, your Stack… after either/both of the above two steps have set a directory definitively:
2016-06-21 09:56:27.328 RapidWeaver 7[4867:78845] Themes directory path is: ~/Dropbox/Apps/RapidWeaverAddOns
Good luck!