If the values for your IN clause are dynamic, you will need to prepare a clipboard page with one or more value lists that hold the values for your IN clause. A Data Page is a good way to prepare these values if they are driven by reference data / data from another system of record.
If the values for your IN clause are fixed, the article quotes what I thought was true in that including comma-separated constants in the Value field for an Equals comparison also yields IN clause behavior. See below for what is quoted:
Commas correspond to an OR test: If the Value field contains two or more entries separated by commas, the comparison is true at run time if the value of the Column field equals (or is greater than, or is contained in, and so on) any one of the entries.
Lastly, depending on how variable the number of members of your IN clause is, don't forget that an IN clause is a simplified OR statement.
A IN (X, Y, Z) ... is logically equivalent to A = X OR A = Y OR A = Z
... but given the above options for dynamic or fixed usage, it seems you don't need to revert to this.