QuickFile does support feeds for more than one account for the same bank but only where the accounts are accessible via the same login on the bank side. I don’t know whether this limitation is imposed by QuickFile arbitrarily or if it is inherent to the way Open Banking operates.
Are both accounts configured in QuickFile as “Barclays”? A common problem I’ve seen other users reporting here is that if the bank name on the settings for that bank account in QuickFile is “other” then you don’t get the option to connect an Open Banking feed, you have to set the right bank name to make the option appear.
Further to what @ian_roberts has said when you make the connection for Open Banking you need to make sure you allow both accounts at this point because there is only one Open Banking connection. If you have set it up and only allowed access to the one account then you would need to revoke and then re-instate the link.