When designing for web apps, breakpoints, and screen sizes are a bit different from viewports on mobile. Users have the capability to decrease or increase the viewport size creating viewports very far apart from standards.
If you were able to set a min & max width for regular frames, you could, for example, create breakpoint templates that could be expanded or shrunk in the range of that specific breakpoint. Helping designers validate designs for viewports range and not a static dimension. You could also include a grid for each breakpoint and change it with variables and the child frame could scale according to the range of each breakpoint.
