copying brokerage transactions

It's not clear why you needed to create a new Quicken account for JP Morgan. I would have thought you could just have deactivated the existing account for download (and probably cleared fields like the financial institution name, account number, etc.), then pointed the download from JP Morgan to the old ("existing Quicken") account. But, assuming the die is cast ....

You can cut, or copy, then paste, from one investment account to another ... but only one transaction at a time. [I have no problem doing this in Q2008 or Q2010.]

The only way to "move" multiple investment account transactions from one Quicken investment account to another investment account is to export the "from" account to a QIF file, then (assuming your Quicken version is later than Q2004) follow the instructions in the post below to import that QIF file into the Quicken "to" account (then delete the old Quicken account).

But I don't see why you need the transactions from the old account in the new account. Why won't just the holdings be sufficient?

You can "transfer" your holdings from one Quicken to another, using the Quicken "Shares Transferred Between Accounts" pseudo-transaction. It will "Remove" the shares from the old account and "Add" the shares (one Add Shares transaction for each "lot" transferred) to the new account ... preserving your cost basis in the process.

Yes, Quicken gives the Add Shares transaction a "transaction date" equal to the date of the transfer. But it gives the Add Shares transaction a "Date Acquired" the same as the original (transferred) lot was acquired in the "from" account. Usually both dates are just what one would want.