How to save and manipulate an already plotted graphic

Question

I have a figure which took some hours to create in Mathematica. I assigned it to a variable myplot, i.e., myplot = Plot[..]. Now I want to turn off my computer, even though the legends in this plot are not as good as I wish. I want to be able to change them later.

In Matlab I used to save the figure as a .fig file. Later I was able to open the .fig file and do any manipulation. How is this done in Mathematica? I dont want to spend hours and hours again to create the same figure with better legends, etc. My main concern is to be able to manipulate the legends of the figure without plotting it again with the new legend definitions.

Here is my try without any success:

Show[myplot, PlotLegends -> SwatchLegend[Placed[LineLegend[{Blue, Red, Green, Orange, Black, Cyan}, {"\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \\(0\)]\), \(c\),n]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \\(c\),m]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \\(c\),a]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \\(c\),h]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \\(c\),c]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \\(c\),\(\*SuperscriptBox[\(c\), \(*\)]\)]\)"}, LabelStyle -> 21, LegendFunction -> (Framed[#, RoundingRadius -> 2, FrameStyle -> LightGray] &)], {Left, Top}]]]

Here is the last lines of ctrl-shift+r

Inset[LineLegend[{RGBColor[0, 0, 1], RGBColor[1, 0, 0], RGBColor[0, 1, 0], RGBColor[1, 0.5, 0], GrayLevel[0], RGBColor[0, 1, 1]}, {"\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \(c\),n]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \(c\),m]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \(c\),a]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \(c\),h]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \(c\),c]\)", "\!\(\*SubsuperscriptBox[\(\*SubscriptBox[\(I\), \(0\)]\), \(c\),\(\*SuperscriptBox[\(c\), \(*\)]\)]\)"}, LabelStyle -> 21, 
LegendFunction -> (Framed[#1, RoundingRadius -> 2, FrameStyle -> GrayLevel[0.85]] & ), LegendLayout -> "Column"], Scaled[{0.99, 0.99}], 
ImageScaled[{1, 1}], BaseStyle -> {FontSize -> Larger}, FormatType -> StandardForm]}, AspectRatio -> 0.7, Axes -> True, AxesLabel -> {Style["t", FontSize -> 21], Style["\!\(\*SubscriptBox[\(I\), \(0\)]\)", FontSize -> 21]}, AxesOrigin -> {0, 0}, AxesStyle -> Arrowheads[0.03], BaseStyle -> 18, GridLines -> Automatic, GridLinesStyle -> GrayLevel[0.85], ImageSize -> {583., Automatic}, Method -> {}, PlotRange -> {{-0.5128185731395787, 0.9326363149439076}, {-0.00003110239778374659, 1.51579064969476}}, 

PlotRangeClipping -> True, PlotRangePadding -> {Scaled[0.02], Scaled[0.02]}]

Answer 1

You can actually change the plot even after it has been finished processing. Example

Plot[Evaluate[{Sin[x], Cos[x]}], {x, 0, 2 Pi}]

Place the cursor on top of the chart itself and press Ctrl-Shift-R You'll see the image convert to a Graphics evaluation. You can operate on this item. Let's say that we saved it under

g = Graphics[{{}, {}, {RGBColor[0.368417, 0.506779, 0.709798], 
     AbsoluteThickness[1.6], Opacity[1.], 
     Line[{{1.2822827157509358*...

I can later add new options to the Graphic. Example.

AppendTo[g, LabelStyle -> Directive[Blue, Bold]]

Or replace already existing options.

g /. Unevaluated[AxesLabel -> {_, _}] -> 
  Unevaluated[AxesLabel -> {"X Axis", "Y Axis"}]

You can of course change the command directly.