Secondary PC temporarily disable

New to Multiplicity, using the Trial version to try out, and pretty good so far, simple as I like, couple of useful advanced features, just a few bits I want to ask/suggest.

I use KMs with my laptop (Win7), 2PCs (Win7, Vista Ultimate [being upgraded soon] and sometimes join my Tablet (Win10) (All x64)

Is there a way to 'lock' out secondary PCs?

As I mainly use my Vista PC as Primary, I sometimes don't need to access my other 3 Computers, but still need/want them running, I would like to see a way where I can stop the KM from swapping, so I am only controlling the primary, or just the primary and laptop, or Primary, Laptop and Tablet, etcetc, I can't find a way to 'lock' the KM in the current version.

What would be nice is something like Tickboxes in the right click menu in taskbar, so I can just untick a machine when I don't want to control it.

Moving onto the second question, I noticed when I needed to swap my primary to the laptop, I had to sign up for a new trial.

If and when I purchase Multiplicity 3 KVM, will I just be able to swap my Primary as I please, just inputting the 1 Licence into each as I need it? ( I don't mind if I have to input the licence every time, as I mostly stick to the Vista PC Primary, but maybe once a week or fortnight I need to swap to the Laptop as Primary)

Thanks in advance.