Here's another cool tip that hadn't occurred to me before: moving your non-NI-registered libraries into the Factory Content folder so you can load everything from the Libraries tab.
Personally, I never use the Libraries tab because too many of my favorites aren't there. But it's a good tip if you do spend most of your time on the Libraries tab.
Now, I know what you're thinking: I don't want to move my libraries around because it'll break existing projects. No problem - just create a symbolic link. Your projects will still find the libraries because they haven't moved. But they'll also show up on the Libraries tab.
Here's how I added all my Indiginus libraries to the Libraries tab. These are DOS commands you type into a command line window. In this example, my libraries are all on my E: drive under the top-level folder "Libs".
e:
cd \libs\kontakt factory library\instruments
mklink /D Indiginus e:\libs\indiginus
This works by fooling Kontakt into thinking my Indiginus instruments are part of the factory content. Note that in my case I had to use a symbolic, rather than hard, link like I would if I'd wanted to point to a separate disk volume. Use /H instead of /D to point to an instrument that's on a different drive than your factory content.