Sure would be nice if the BSS Preview server opened and maintained a connection to a separate browser tab for each BSS design tab.
I'm working on a project that requires me to have 2 BSS design tabs open (one for BS3 & another for BS4) -- make a change to the BS4 and see how it compares to the BS3.
I can open a new browser tab for each but when I make a change to the BSS BS4 tab, both browser tabs show the BS4 changes and I have to go back to Preview and open a new browser tab to see the BS3 again. Yucch....
You shouldn't have to do all that. When I have multiple projects open, any time I switch from one to the other in BSS, it automatically adjusts the browser window to whatever project i have open as well as whatever page I'm looking at in BSS. Could be you're over thinking it? Try doing just that. Open both of your projects, then Open a preview window for either one, but just one. Now swap from one project to the other (click the tabs in BSS basically) and now check your browser window. If it doesn't update, hit refresh.
Actually, I would like to have the two browser tabs rather then have to switch back to BSS to see one design or the other. In that way, I could detach each browser tab and view them side-by-side.