You can hide the Company Selection window when you open Sage 50 Accounts. When you select the 'Hide company list on start-up' checkbox on the window, it's hidden when you next open the software.
To reinstate this window, you can delete the SAGE.INI file.
Deleting this file also reinstates any message you've paused in the software. For example, the pause outside current financial year message. Follow the steps in our how to reinstate a message after selecting not to show the message article as each message has different steps.