Adding existing hosts manually

Hi,
I have imported about a hundred machines on one of my clients networks
into foreman and am slowly moving from the concept of every thing is
managed to every thing is actually managed.

 We use salt here and I have a few more difficult hosts, where I cant 

run the salt-minion to autoregister these hosts in foreman. Is there a way
to import the hosts into foreman manually? It is a small number and I just
want to add them to a hostgroup unmanaged, to remind me every day that I
need to actually fix these.

 If I am manually add the hosts in the UI I am afraid I might actually 

re-install them, and that would be bad.

Thanks for your advice.