Multiple viewports - is this feasible?

OK, I am going to start numbering my questions - to keep better track, I guess, I hope.
I am making progress with my Smith chart and planning little ahead.
I like to limit the chart to an essential graph, with very basic scale / precision.
Then I would like to “zoom” to area of interest which I presume can be done by OpenGL “transformation” matrices.
Then I woudl like to adjust the scale to include ADDITIONAL traces.
So for example and simplicity I envision
basic "viewport " with traces .1 and .2
then "zoom in " to see traces
.10 .15. .20
So can I have
viewport “plane” on top of another viewport "plane " with more traces
and just “switch” between them ?

Or is this a good example to implement both stencil and depth buffers ?

I’m fairly sure that this problem doesn’t need either stencil or depth buffers.