That path is that standard sandbox path. It’s dictated by Apple unfortunately. A sandboxed app can’t link to anything outside of that directly without specific user consent.
note: I’m not a fan of this and despite all efforts, it’s very difficult for me to hide my utter disdain for all things related to sandboxing
The good news is that you can move the RapidWeaver addons folder (that gives RW the explicit consent they need to look in another location). To do this open up the RapidWeaver prefs, click the Addons tab, and choose Other from the popup. You can see from the shot I keep mine on the desktop because I tend to use that folder rather a lot.
btw: you might wonder… “Why does RapidWeaver even do sandboxing? Some apps don’t.” You’d be right, but there are longer term strategies probably at play…
NB: I’m just an outside observer, I don’t know the real reasons, and don’t speak for Realmac. But I can take some educated guesses.
Sandboxing is required to get in to the Mac App Store. And while RapidWeaver currently doesn’t ship through the Mac App Store today, I suspect that if the Mac App Store got the update it really needs that perhaps RapidWeaver might like to re-enter the store. Since switching between sandboxed and non-sandboxed is really really really hard – they’re probably choosing to stay sandboxed just to keep their options open.