The products you include in your bundle can either be optional or required.
For bundles with a Single page structure, the optional products of the bundle can be selected in the Optional products section:
For bundles with a Multiple Sections structure, the optional products will be selected in the Sections section:
Your customers can choose which optional products they wish to add to their bundle, but they may still be required to add a certain number of optional products in order to meet your bundle's requirements. You can set these requirements in the Conditions section of the Bundle Editor.
If you'd like to only include a subset of product variants in a bundle, you can do this easily by selecting a variant from the dropdown and adding others as needed:
These variants will then be listed as separate products on the bundle:
Required products will be part of the bundle by default and cannot be removed. You can now select variants of products to be required and even add the required quantity of a product or product variant: