When using this option for the terminal setting, via the gnuplot.ini configuration file, it can cause an error while performing multiplots. At some point during the plotting, Gaston reads out the config-file again and returns the error "You can't change the terminal in multiplot mode" and points at the gnuplot.ini file. The plot will be still generated properly with the flaw, that all settings after the "set term" in the config-file aren´t executed anymore. As a prematurely fix one can simply paste the "set term" command on the last line in the gnuplot.ini.

Windows10
set term qt
Multiplot:

t = 0.01:0.01:10pi
p1 = plot(t, cos, Axes(title = :Plot_1), handle = 1)
p2 = plot(t, t.^2, Axes(title = :Plot_2), handle = 2)
p4 = plot(t, exp.(-t), Axes(title = :Plot_4), handle = 4)
plot([p1 p2 ; nothing p4])

 Warning: Gnuplot returned an error message:
│
│ (process:13548): GLib-GIO-WARNING **: 10:33:58.732: Unexpectedly, UWP app `Evernote.Evernote_10.18.3.0_x86__q4d96b2w5wcc2' (AUMId `Evernote.Evernote_q4d96b2w5wcc2!Evernote') supports 1 extensions but has no verbs
│
│ multiplot> set term qt
│                     ^
│            "C:\Users\lukas\AppData\Roaming\gnuplot.ini" line 14: You can't change the terminal in multiplot mode
│
│
│ multiplot> set term qt
│                     ^
│            "C:\Users\lukas\AppData\Roaming\gnuplot.ini" line 14: You can't change the terminal in multiplot mode
│
│
│ multiplot> set term qt
│                     ^
│            "C:\Users\lukas\AppData\Roaming\gnuplot.ini" line 14: You can't change the terminal in multiplot mode
│
└ @ Gaston C:\Users\lukas\.julia\dev\Gaston\src\gaston_llplot.jl:182

Thanks for this PR!

I am close to releasing Gaston v2.0. Among other things, I have reworked the way multiplot works, in part to get around issues like this one (and others; my approach was far too brittle). For this reason, I will not merge this, and instead will rely on the improved v2.0 code.