Have you looked at the Mendix introduction course? As assignment, you have to build a app, to register trainees to a ScheduledCourse, using a registration entity. This structure of ScheduledCourse <- Registration -> Trainee and the related schedule page. Is technically 100% equal to the Order <- OrderLine -> Product structure (domain model & pages).
Just different naming.
Take a look at: https://gettingstarted.mendixcloud.com/link/courses/introductioncourse
Module 4 & 5
Thank you. This course if very helpful beginner guide.
Tom, the tutorial does give a very well getting-started-guide for any maintenance of two tables having a one-to-many association. But it uses more than one form and not one form as in the vision you described. Have a look at order106.mxapps.io which is sort of finished, but several improvements can still be made. I do think this is more like your vision. I'dd like to invite you to help out making some improvements to this one page maintenance form for Order/orderlines and get to know Mendix better at the same time. If you like that, please send me your email to firstname.lastname@example.org so I can invite you to the order106 project. This will also get you aquainted with Mendix's Project-management and it's code-version-management.