Maybe so - this needs to go in the formula editor (so, click on the fx button) and the field needs to be selected with the field picker. See attached screenshot. In this sample, I wanted to set a default value for a field, so in the field's properties, I clicked on the fx button, which opened the formula editor. You can pick the concat function using the insert function button, or just type it in. Select the field using the insert field button - you'll see how it now shows as underlined in the final formula.