As far as simulation goes, I can handle ngspice interactive simulator to validate an design. But there are cases where I need to format the plot, chart or whatever is required by a design report. So, what is the comunity using for post-procesing ngspice results, and what output format to use, how to import the data?
Once saved in a Project, a WaveForm window can be exported as a .pdf, .png or .svg file into your browser window. This can then be saved to your device so it is easy to create professional quality documentation.
Searching internet on "ngspice waveform viewer" I found: post-simulation data processing with Qucs-S and Octave