Old, inactive Suppliers can clog your lists. You can delete them if you have never entered any type of transaction for them. Edit the Supplier and click Delete at the bottom of the screen.

But if you have entered any transactions, Manager will not allow you to delete a Supplier, because doing so would also delete all related transactions. Instead, you can make a Supplier inactive. Edit the Supplier and check the Inactive box. Click Update and the Supplier will no longer appear in active lists:

If the Supplier ever returns to active status, scroll to the bottom of the suppliers list, where you will see the Supplier’s name in light grey text. Click Edit next to the Supplier’s name:

Uncheck the Inactive box and click Update.