I only have 4.01 and 4.02 right now.

I never noticed this, and was wondering when it was added, or if I just
completely missed it over the years...

Open a Policy object, upper right tab bar, has Insert (policy, group,
action, etc), Comapre, Deploy, Simulate, Namespace editor, up, down,
trace, help.

In the Insert there is a down arrow, which if you drop down, you get a
bunch of choices.

one is Include. I only knew about this from Holger Dopp's SAP HR
drivers. However, I never noticed it in the UI here. Neat!

Anyone know when that was added, or if it has been there all along?

Include is pretty cool. Looks like:

<include name="..\..\Library\lib-LogFileSpec-V2" notrace="true"/>

Basically it executes the included policy in line where included, and
variables available before it are available to it locally, and variables
it touches, are available after (I am pretty sure).

Which is really helpful. But rarely used.