You group several columns under one shared heading with Column group in Edit table layout. The columns in the group stay together, and you can move and color the whole group at once.
How to do it
Click Table layout at the top of the table.
Open the menu (three dots) in the heading of one of the columns that should be included.
Select Column group. A window opens.
Give the group a name, for example Costs.
Under Columns in the group, tick the other columns that should be included.
Click Done, and then Save layout.
Good to know
Drag the group heading to move all the columns in the group.
You can give the whole group a background color in the same window, so it is easy to find again.
To rename the group, click the pencil next to the group name in the heading.
To dissolve the group, click the cross next to the group name. The columns remain in the table.