Some questions should only be asked after a particular answer. A burger on its own needs no side, but a burger combo needs a side and a drink. In Shop+ this is done with Follow-up modifier groups: a setting on a modifier option that names other groups to show once that option is selected.
The end result
A Classic Cheeseburger at $9.50 with an optional question, Make It a Combo. If the customer chooses Make it a combo (+$3.50), two more questions appear: Combo Side (French Fries, Onion Rings +$1.50, Side Salad +$1.00) and Combo Drink (Fountain Drink, Iced Tea, Milkshake +$2.00). If the customer chooses Sandwich only, those questions never appear.
What you will build
Two follow-up groups: Combo Side and Combo Drink, each required, pick one.
One trigger group: Make It a Combo, optional, pick one, with the follow-up groups set on the combo option.
The trigger group attached to the product.
Step 1 – Create the follow-up groups first
In the left sidebar click Shop+, stay on Products, click the Modifiers tab and click Create. Name the group Combo Side, set Minimum Selection to 1, Maximum Selection to 1 and Selection Type to Single Choice. Add the sides as items, with a price on the premium ones, and click Save Modifier. Repeat for Combo Drink.
The follow-up groups must exist before you can select them in Step 3, which is why they are created first.
Step 2 – Create the trigger group
Click Create again. Name the group Make It a Combo. Leave Minimum Selection empty so it is optional, set Maximum Selection to 1 and Selection Type to Single Choice.
Add two items: Make it a combo with a price of 3.5, and Sandwich only with no price.
Step 3 – Set the follow-up groups on the combo option
Click the Make it a combo row to expand it, then click More settings. At the bottom of the panel, in Follow-up modifier groups, select Combo Side and Combo Drink. The note under the field confirms what it does: shown only after this option is selected. Click Save Modifier.
Step 4 – Attach only the trigger group to the product
Open the product, scroll to Product Modifiers and select Make It a Combo in Select modifier groups. Do not attach Combo Side or Combo Drink to the product directly. If you attach them, they are asked every time, whether or not the combo is chosen. Click Update Product.
Step 5 – See the result
Before anything is chosen, the customer sees only the Make It a Combo question and any other groups attached to the product.
After Make it a combo is chosen, Combo Side and Combo Drink appear directly beneath it. Because both are required, the item cannot be added until a side and a drink are chosen. The price now includes the $3.50 combo upcharge, and any upcharge on the side or drink is added on top.
Other ways to use follow-up groups
Add a protein, then ask how it is cooked. An "Add Steak" option on a salad opens the Steak Temperature group.
Upgrade, then choose. A "Premium Side" option opens a list of premium sides.
Gift wrap, then choose the paper. A Gift Wrap option opens a Wrapping Paper group.
Engraving, then the text. An "Add Engraving" option opens a Text Box group for the wording.
Tips
Make follow-up groups required (minimum 1) when the answer is needed to fulfil the order. An optional follow-up can be skipped.
One follow-up group can be reused by many trigger options. Combo Side can sit behind the combo option on every sandwich.
Price the trigger option with the combo upcharge and keep the standard side and drink at 0, so the combo price is clear.
Common questions
How do I set up a combo meal? Create the side and drink groups, then a Make It a Combo group whose combo option lists them under Follow-up modifier groups.
Why are the side and drink asked on every order? They are attached to the product directly. Remove them from Product Modifiers and leave only the trigger group.
Why do the follow-up questions not appear? Open the trigger group, expand the option, click More settings and check that the groups are selected under Follow-up modifier groups.
Can an option have more than one follow-up group? Yes. Select as many as you need.