UK unit trust, mutual fund, editing FUND in price editor?

[Adam Funk]

I'm trying to account for a UK unit trust, which I think is equivalent
to a "mutual fund" in US accounting and in GnuCash.  Right?

So I created an account in the asset subtree of type Mutual Fund, and
created a commodity of type FUND (which I think came up
automatically).  I set up the initial Buy transaction smoothly against
"Opening Balances" (I had this before I started using GnuCash and am
now carrying out some retrospective improvements in my accounting).

The unit value has now changed, and I think that in order to reflect
this I need to add the current price in the Price Editor --- right?

But when I open the Price Editor the type FUND and the commodity I
created are not visible.  What am I doing wrong?

Thanks,
Adam