You could use an Assistant to easily create formulas, for example to summarize different fields.
You could open the formula assistant in the context menu of EVERY textfield, which show the small blue button on right side.

Create and make use of formula

The big text field on top of the popup will get your formula with “Variables”, like Placeholders. For every variable you can define the value, which is used after you leave the field.

For example, if you want to summarize 3 fields, enter the formula Field1+Field2+Field3 and leave the formula textfields with [TAB] key or something else.
The assistant will parse your formula and extract every variable you use. In this case, you can define the values for the variable “Field1”, “Field2”, “Field3” independently to your fieldvalues.
During execution, the Variables will be replaced by content of the single variable text fields.

Because of Mathematical execution, it is important to only use alphanumeric variable names.
So you cannot use “Variable_Name_123”. Instead you should use “Variablename123”. Because name of variables have no impact on formula, this will not limit the formulas.

Now you could set the value of every variable individual. If you really want to summarize 3 fields, choose the correct fieldvalue variable within each text field.

If you click on “Save & Insert Formula” the formula will be saved and the shortcode added to the textfield you use to open the assistant, or the formula is selected in list.
You could set a name of the formula, which is shown in field set list, when selected “Formula” as set type.

edit a existing formula

If you want to modify a already existing formula, you need to open the task configuration, which use the formula, select the shortcode with your mouse, open context menu and click “Formula Assistant”.
The system will recognize you select the shortcode, extract the ID and load the existing formula.