As I understood, you have two entities Customer and CustDetail, and an association between the two of them and should be one to one.
Now you need to enter the info for the first form which is Customer and then on save button take you to the next form right ?
For me in this case I would make the save button to call a microflow and in this microflow I will create new object for the CustDetail and set the association for it to the parameter that I got from the previous form.
And pass the new created object to the next page using Show Page Activity.
Then in the next form you save the changes after filling the required fields.
I hope that helped you.
For the edit part you have to change the microflow
Check if the parameter have an association, if the association is empty then it’s new object if not then edit old one.
Instead of creating new object retrieve by association the CustDetail and send it to the page
If you still have any problems just be sure that you are committing all changes in the second form
You need to go with using of associations between the two entities.A associated table will be created for the two enitites in the database you can checkout the associated table through the help of console>Advanced>start builtin DatabaseViewer and then select the associated table from the list tables and click execute on it.
You can see the data of associated table.
Hope this helps.
You have to utilize the power of association here , if customer can have multiple details you can use 1-* .or if one customer will have one details you can use 1-1.