This may be somewhat obvious, but maybe not to everyone: You can write-protect the Service Manager Dialog .ini file to keep it from storing hostnames in it's history list.
Why would you want that? Well, having the previous host names in the dropdown may be a convenience feature, but for me the current implementation does more harm than good. Apparently if you ever typed a name that doesn't exist as a DNS name, or has no active UC4 service (or it had one, but no longer), I find the Service Manager hangs for long stretches of time:
Pictured: a site that's obviously not exposing a UC4 agent
(yes, it's German, but we all know this all-to-common message ...)
... and worse, when you close it, and open it again, it will try the (now) invalid site again, and thus won't appear to start at all. So if you're like me, you might click the icon repeatedly, and once it eventually starts, impatient-me ends up with 17 instances of Service Manager Dialog. Which will then proceed to hang again.
A sort of solution? Open the .ini file with notepad or some text editor, clean out the lastname= and Host01= and all following Host sections at the end, then save and write-protect it. Now SMD won't save any settings, but in turn it will start reliably near instantly all the time.