Setting up accounts using a second file

I’m currently tracking some of my investments via @brucanna’s inventory method, and some by just keeping track of the balance of the accounts (I wanted to try each workflow while giving Manager a shakedown tour). I’m considering moving all of my investment tracking to the inventory method (although I guess with an Investments tab coming soon, maybe this is unnecessary work). But it still sparked this thought:

Given that i have my books accurate, I’m loathe to start moving things around piecemeal. Is there any reasonable way to:

(1) Set up the investment account inventory items in a completely separate Manager file (it’s basically a single account and its associated equiities), and then
(2) Migrate them to my real manager file in one go? (Doing something like “copy/pasting through Excel” would be a fine solution, if that works.)

I’m exploring “Batch Create” now.

Just double checking: if I’m reading the guide correctly, the expense that’s posted when an inventory item is sold is taken from its average cost, not from its purchase price, correct?

Correct. Purchase price defined for an inventory item is just a shortcut for prefilling forms. The cost of any purchase contributes to average cost.