I've got two projects I've been working on lately (1st is a one page site so far and the second is a larger, more complicated affair) and wanted to share some code from one to the other by opening both side by side. Upon opening the second larger site, bootstrapstudio locked up and won't allow any further action.
I don't know if this is what you're trying to do since I'm not sure what type of code you're trying to share, but one of the little features that I discovered by accident this morning is that you can share code with other pages of your document by right clicking in the Overview tree on whatever part of the tree/code you want to share (easier to share a column/row/custom code setup than just a bit of code text, you can use a notepad for that transfer if you just want to copy some code text.
If you want to share something bigger with another project, you can create a Library with it and that will show up on all projects. Then drag it where you want it and edit away.
That's about all I can think of for sharing code, but it's pretty simple all the way around so far as I can tell at this time. Still new to the app, but finding lots of neat little features as I play with it or ask questions. :)
Sorry for replying so late, we were busy with the latest update and I didn't have time to keep an eye on the forums.
How did you display the two designs side by side? Did you start a second instance of Bootstrap Studio somehow?