When dialog is opened the checkbox should be selected by default.
Steps to achieve this in touch ui
Continue readingTag: Touch UI aem
AEM provides OOTB multi-field in which only one widget/field can be configured as part of the multi-field.
For example, have a look at the OOTB list component
(/libs/foundation/components/list/cq:dialog/content/items/column/items/
setStatic/items/well/items/pages) which only has a single field in a multifield.
In most cases this might not suffice your requirement. You might need a composite multi-field with 2 or more fields as part of the multi-field.
To achieve this there are multiple options. You can choose to go with either of them.