Welcome to the forum!
I don’t think there will be any member who can give you detailed step-by-step instructions. We are not Readsoft (Lexmark) consultants and have learned through trial-and-error and the school of hard knocks. Consequently, we are unlikely to have detailed instructions. Nonetheless, we can provide general information about how we have solved a particular problem. It is important to note that we are not supported or endorsed by Lexmark.
What forum members can assist with is providing a balanced view between what is technically possible (with enough money you can get a computer system to do anything you want) and what is business process feasible.
My first thought with your requirement is that you do not have a First Time Verification inbox. This means that Verifiers (unless they have an extraordinarily good memory) will not know which invoices they have meticulously taught the fields for. So they will constantly try and make every invoice perfect when they only need to perform this task once when the invoices is interpreted the first time.
The second thought is why you would need to allocate invoices to Processors from within the Invoices module? We allocate invoices to Processors once they move to the ERP (SAP System). The system automatically does this based on the first letter of the vendor name. For example, Processor 1 does vendors A-K. The work of having to sort invoices so they end with the right processor at the Invoices end of the process might create more work than is necessary.
When we went live with Readsoft, we had a few thousand invoices in Verify. But as we got knowledgeable about using the system well, allowed the autocomplete indicator to flow invoices through, set up autoposting into our ERP, optimised our major vendors, there is rarely more than 100 invoices in Verify at any one time.
Further, since our AP operators know which letter Vendor they process, when they are in Verify they simply sort the list and do a bulk select of their vendors only.
You probably would be better off spending the effort on getting invoices to move quickly through the Invoices module into your ERP. This is better done at a global level rather than at the individual processor level. If you silo up your Invoices module you are likely to have varying degrees of efficiency in pushing invoices into your ERP.
To create your folders, you would do this from the Manager module > Settings > Inbox configuration. I have attached a screen shot showing our folders for one of our entities. There is other discussion on the forum http://readsoftuser.forumchitchat.com/post/invoices-inbox-configuration-how-we-made-it-easier-for-the-verifyers-6950487
Do this in your Test environment first.
As a tip, using Manager take a note of the number of invoices at the top of the table. This is the total number of invoices that should be in Verify. As you make your changes, sum the total of invoices in each of your inboxes in Verify. If the total does not tally with Manager, then keep tweaking the Inbox configuration and restart Verify to review the change.
If you are absolutely wedded to the requirement to allocate invoices to processors from within your Invoices module then there are a few ways you can do this. In the Inbox Configuration tab in Manager there is a tab for specifying user-defined variables. You could also create email addresses for each of the Processors then use Collector to process into the relevant folder (all your invoices would need to come in via email). You can create Jobs in Manager for each processor but you would need to sort all your inbound invoices accordingly. In Manager, you can copy your Invoices profile and have separate Invoice profiles for each processor group. These are just general tips. If you need step-by-step guidance or advice on how best to allocate invoices in the Invoices module then please refer to Lexmark consulting for further assistance.