[FEATURE] - allow selection of line type "step" from command line.

[jjanice]

What's the problem this feature will solve?

I'm a fan of trace -p PV and would like to be able to specify line type step at the same time. When plotting digital/binary, step is easier for my brain to parse.

Describe the solution you'd like

please provide an argument to specify line type step at command line. trace -p PV -x step

Additional context

No response