How do I change Timesheet columns?

You can modify the grid settings (column sort order and which columns are displayed) in the Timesheet tab, and these settings can be saved or reset.

Start by navigating to Settings > System Settings > Features > Misc and ensure that Enable grid personalisation is enabled. 

Go to the Timesheet screen and right click on a column heading to bring up the Sort/Column Select menu. 

Click on the gear icon (arrowed) to display the Grid Settings menu where you can Save or Reset the current column settings.

Apply these grid settings to all users by navigating to Admin > User > [select your User record] > Settings and click the button Apply this users grid settings to all users.