Custom columns let you add additional data to your Profit and Loss and Balance Sheet. To enable a custom column, toggle on the Custom Column property in a report.
The options for a custom column are:
Custom Column Data
the prior period data
% of Income
% of the current period's income (P&L only)
% of Expenses
% of the current period's expenses (P&L only)
When comparing against a prior period, you can also add $ Change and % Change columns.