Hi,
The way that this can be accomplished in ODK Survey is by using subforms. More information about subforms can be found at ODK-X Survey — ODK-X Docs. The grid representation is not in the subform example. We do have an ODK Survey example of a grid in the app-designer repo at app-designer/app/config/tables/gridScreen/forms/gridScreen/gridScreen.xlsx.
However, if you are proficient with HTML and JavaScript, you could create an HTML page and use our injected JavaScript Interfaces in ODK Tables to add a row dynamically (ODK-X WebKit — ODK-X Docs). More information about ODK Tables is at Trying Out ODK-X Tables — ODK-X Docs.
Clarice