Input actual values manually
If you do not have data sources set up for certain rows, but you wish to show actuals values, you can input them yourself.
The first way is to manually hardcode actuals values into the cell.

The second way is to create formulas in the actuals cells. This is relevant if the actuals value can be derived from other rows in the budget, e.g., revenue growth % or margin %.

In both cases, cells with overrides will show a small dark mark to indicate that the actuals value has been altered.
If you delete the override, the cell will return to its original data source value, which will be 0 if there is no connected data source.