accounting for managed investment accounts

[gnucash.133518b at telus.net]

Imagine I have a real-world personalized professionally-managed 
investment account of the sort often referred to in Canada as a "managed 
account" or "discretionary account". I am not consulted on the buying 
and selling of the assets and cash within the account. As this is not a 
mutual fund, my external transactions with this account are in dollars, 
not shares. Similarly, my tax consequences relate to external 
transactions with this account, not transactions that are internal to 
the account.

I want to add a corresponding investment account created in my GnuCash 
book, but how do I do this? I don't think I can use either of the 
"stock" or "mutual fund" account types because those appear to be 
strictly denominated in share units. The number of different assets in 
the managed account are too many and too often changing for me to want 
to try tracking them individually in GnuCash and the whole point of such 
an account is to manage it as a (more or less) black box.

After reading Peter Selinger's well-known "Tutorial on multiple currency 
accounting" as well as "8.7 Selling Shares" in the GnuCash Tutorial and 
Concepts Guide I have a very tenuous understanding that realized 
gains/losses need to be accounted for with investment accounts. It is 
not clear to me from my reading why it is that when tracking individual 
stocks that one must always manually calculate and enter profits for 
individual stock sale transactions such that they are sourced by an 
Income:Capital Gains account but that this does not also apply to 
currency exchange transactions. Assuming someone can tell me how I can 
even implement my managed account in GnuCash, how do I account for its 
realized gains?

For unrelated reasons I will have trading accounts enabled. How does 
this changes things, if at all?

I also have a variety of loose investment assets within a real-world 
portfolio account I manage on my own. I am not yet sure that I want to 
track those individually as stocks in GnuCash either, but I at least 
need to account for them as a group, so I think this would be pretty 
much the same thing as the managed account. It seems to me this would be 
an approach that a lot of people would go for if someone could give us 
an easy-to-understand description of how to accomplish this sort of 
thing correctly.

In case it wasn't already painfully obvious, keep in mind that I am 
totally new to GnuCash and accounting concepts in general.

Carl