The Processes tab ships with 15 data columns plus the graph column. Use the column settings dialog to pick the ones you want.

Right-click any column header on the Processes tab and choose Column settings....
Changes apply to the tab as you make them.
The first column on the tab (the process name) cannot be hidden and cannot be moved out of first position.
OK keeps your changes. Cancel reverts to the layout that was in place when you opened the dialog. Layout changes are saved with the program's settings.
The same dialog is used for the Servers and User sessions tabs. Each tab has its own layout stored separately. The Application log tab has a fixed set of four columns (Time, Level, Category, Message) and does not use this dialog.