Is there a setting in Quicken that hides selected portfolio positions?

"the missing security isn't your core money market fund is it?" No. It is a money market fund, but it is listed along with all other holdings without any "core" or related designation.

Ah, but the Vanguard Federal Money Market Fund (VMFXX) is the primary default settlement fund (core fund) for most Vanguard brokerage accounts. And that would explain why Quicken is setting the holding of VMFXX to zero with the placeholder transaction, irrespective of your attempt to manually add shares. Vanguard is reporting your VMFXX holdings as cash rather than a shares of a security.

The question is: is the value of your VMFXX holdings displayed in the Portfolio as all or part of a Cash line as the last row in the list of holdings. If yes — there is a Cash line which includes the value of the VMFXX money market fund — than this is considered standard behavior. If not, you have a problem to discuss with Quicken Support. There are other threads which describe a Fidelity core money market holding being part of cash, but reinvested dividends being download and posted as reinvested dividends instead of as cash dividend; if you're experiencing that with the Vanguard money market fund, that would be a different problem to bring up with Quicken Support

Fidelity does not report cash for the account, a 401(K). (A related problem I still need to address is that Quicken is showing a cash balance while Fidelity has no position for cash.)

@FC Wolf Yes, this is exactly what I'm describing. On your Fidelity statement, it shows shares in a money market fund. But when Fidelity downloads to Quicken, it translates core money market funds to cash. So in your Quicken portfolio, you have a Cash line which doesn't exist on your Fidelity statement; on your Fidelity statement, you have a money market fund which doesn't exist in your Quicken portfolio. Are those two amounts the same?

I don't use Fidelity; I use Schwab. In some of my accounts, my Schwab statement shows a section for Cash and Cash Investments; it includes "Cash", "Bank Sweep (TD Bank)" and "Money Fund non-sweep (SWVXX Money Market Fund". When I compare my monthly statement to Quicken, I need to add together the "Cash" and "Bank Sweep" amounts on the statement to compare to the "Cash" line in the Quicken Portfolio. Other brokerages report things slightly differently, but the concept is similar: one money market fund designated as the core or sweep found for the account may appear on the brokerage statement with the fund name and balance but will appear in Quicken as simply all or part of the Cash amoount.

@FC Wolf What is the difference between the cash value reported in Quicken and the value of the money market fund reported by Fidelity? Are there any other money market funds in this account which could account for the difference?

I understand there is no cash reported in your Fidelity account. What I'm telling you is that when the core money market fund's balance is reported to Quicken, it is shown in Quicken as cash rather than as a separate security. If those two amounts are the same, then it's not too big a deal for anyone to deal with. But if those two amounts are different, as you're saying, then some additional digging is needed to find out why Quicken is showing a Cash balance which doesn't match the money market fund value.

So my first thought is wondering if there is another money moarket fund which could be adding to the cash balance in Quicken. If your other investments are securities other than money market funds, the I would next turn to the transaction register for the account to look for clues. Is the running balance in the transaction register equal to the Cash amount on the Portfolio screen? As you scroll back in time, was the balance always zero, and recently became non-zero? If not, when did it become non-zero — and what transactions are generating and/or consuming cash?

When one investment is sold another must be bought for the proceeds. Nothing flows into or out of cash.

Got it. But Quicken has no way to exchange 'x' shares of security XYZ for 'y' shares of security ABC in one transaction. I think of every such exchange as a sale of a security creating cash followed by a buy of a security using up the cash. Your Fidelity statement may not show that two-step process, but I'd expect that's the way it would be reported to and tracked by Quicken. So when you look at your transaction register for the last time you exchanged some shares of one security for some shares of another security, how is that recorded in the transaction register? Are there two transactions for the Sell (creating a cash balance) and then Buy (using up the cash balance)?

@Jon Okay, that souunds a bit different than the IRA accounts I've had at Vanguard and Schwab, but the key here is that Quicken account is showing cash. I was trying to get at where that cash balance is coming from. Maybe Fidelity isn't translating a share exchange in the account correctly for downloading to Quicken. Maybe they, or Quicken, isn't distinguishing this account from other types of brokerage accounts. That's why I wanted to know what was happening to create cash in the transaction register.