"Please, Quicken, give us a keyboard option to set transaction status, especially in investment accounts!"
That option already exists; it's called "Reconcile".
You can initiate a reconcile in most accounts by selecting "Reconcile" from the Account Actions dropdown. You can initiate a reconcile in most accounts by holding down CTRL while pressing "r". You can place an icon in the Quicken Toolbar to click when you want to initiate a reconcile (if no account is open when you click that icon, Quicken will ask which account you want to reconcile).
And in non-investment accounts, you can select multiple transactions (as you would select multiple files in Windows Explorer); then right-click a selected transaction, place your cursor on "Reconcile" and choose "Reconciled".