Entry Form- Using Parent and Child Collection

i have a 1 parent and 2 child collections, and I need to create a data entry form
considering that the form must fill the parent and 2 child collection

how to create such form?

In this case, you will need to create 2 forms. The first firm will create the parent and then 2nd form will create the child. You can call the 2nd from after the first form save success.

There is currently no way to create both of them from the same form (we had this concept of nested forms to handle this scenario, but we removed it as it was much complex)