You can always go back and view or edit a formula that was added to a search. Do this by selecting the edit icon next to its name in the columns listing. To view or edit an existing formula in a chart:
Navigate to the chart whose formula you would like to edit. If the chart is within a board, select the ellipsis menu for that chart and click Edit.
Scroll down in the data panel on the right-hand side of the page to the formulas section. Expand the formulas section in the data panel if necessary. You can see a list of all the formulas in the chart.
Hover over the formula you want to edit, select the ellipses icon, and click Edit.
View or edit your formula in the formula editor.
If you edited your formula, select Save to save your changes; otherwise, select Cancel.
Formula elements are color-coded by type and can include the formula operators and functions (blue), the names of columns (purple), the names of parameters (green), and/or constants (black).