Qrew LegendInteresting Question. Basically you are asking how to ensure that users who have permission to add records, can only do so on a form and not on Grid Edit.
There is not a way to hide those 4 blank rows at the end of the Grid Edit report.
One work-a-round would be to initialize a field called [How Entered] with the text value of say "Entered on Form". So just create a formula field with that formula and then convert it to a text field type.
Then put in a form rule that say when [How Entered] is not equal to Entered on Form change it to Entered on Form.
Put that field on the form either as Read Only or in a section hidden by a form rule.
Then go into a Custom Data Rules in Advanced Settings for the child table and make an error message formula that says
IF([How entered] <> "Entered on Form", "Not allowed to Enter Data in Grid Edit")
You will find that when you go to save the record in Grid Edit that users' attempts to add children via Grid Edit will be thwarted with that error message displaying as a prompt of what to do.
I'll have to give that a try. I'm not sure it works for every case, just because I found that if you activate a record that has a required field it doesn't easily let go. As I recall, during testing I typed in data to a field and the deleted it to see what happened, and it kept throwing the required field error and essentially wouldn't let me back out of it.
I think another way to handle it could simply be not to display in edit mode but get give the user an edit button in the row on a report line and either give them a pop up or open in same window.
