Perhaps I am using the guide in an unconventional way, but it would be handy to be able to align the guide to a frozen bit of backbone without having to unfreeze it first.

Working on my first guided puzzle, I found myself freezing the good bits of the backbone and moving/"global wiggling + bands" everything else. During the global wiggle the frozen backbone can still shift off of the guide. To realign the guide after a wiggle I had to unfreeze the backbone, realign, then freeze again. After several repetitions the unfreeze/align/refreeze cycle becomes tedious.

Even if this is a silly process, I am unaware of a reason why you should be prohibited from aligning the guide to a frozen backbone, since aligning the guide does not require modification to the protein.