Since updating Manager, the description column is no longer visible so I can’t add text to the line.
Is there any way I can do this without having umpteen different parts on the system?
EG. Oil - could be hydraulic, engine, gear etc. etc. I would prefer having one part named Oil and add the type to description if that makes sense. I currently only use Manager for invoicing but will in the future use it for all our accounting but not yet.
That will get you into trouble. When you start using the program more fully, Manager will treat all these different types of oil as the same exact inventory item. You need different inventory items for each type of oil if you are going to buy, stock, and sell them as inventory and use the program to track quantities.
Note, this issue is completely independent of making descriptions show for line items. @sharpdrivetek has already given you the answer for that.