This has been discussed many times in the forum previously. Search the forum to read those discussions. Briefly, the reason something like this is not implemented is because there are many paths to an individual transaction. The concepts of Next and Previous (or Back) will mean different things to different users, depending on how they arrived at a transaction. They might mean Next/Previous:
- Reference number
- Creation date
- Due date
- Unpaid transaction (for invoices)
- For customer or supplier by reference
- For customer or supplier by date
- In workflow (for example, when a sales quote is copied to a sales order, which is then copied to a sales invoice, then to a delivery note)
You have suggested your personal preference. Others have different preferences.
Additionally, Manager functions as a browser. Back means specifically “back to the previously displayed page.” Next does not mean anything until you go there. A browser cannot predict what page you want to view next.