Legends size using "Show" function

Question

I have two graphs:

Plot[{x, x^2, x^3}, {x, 0, 3}, PlotRange -> {0, 27}, 
 AxesOrigin -> {0, 0}, AspectRatio -> 0.75, 
 PlotStyle -> {{Black}, {Black, Dotted}, Black}, 
 AxesLabel -> {Style["x", 18], Style["y", 18]}, LabelStyle -> {13}, 
 PlotLegends -> {"func. 1", "func. 2", "func. 3"}]

Show[
 Plot[x, {x, 0, 3}, PlotRange -> {0, 27}, AxesOrigin -> {0, 0}, 
  AspectRatio -> 0.75, PlotStyle -> {Black}, 
  AxesLabel -> {Style["x", 18], Style["y", 18]}, LabelStyle -> {13}, 
  PlotLegends -> {"func. 1"}],
 Plot[x^2, {x, 0, 3}, PlotRange -> {0, 27}, AxesOrigin -> {0, 0}, 
  AspectRatio -> 0.75, PlotStyle -> {Black, Dotted}, 
  AxesLabel -> {Style["x", 18], Style["y", 18]}, LabelStyle -> {13}, 
  PlotLegends -> {"func. 2"}],
 Plot[x^3, {x, 0, 3}, PlotRange -> {0, 27}, AxesOrigin -> {0, 0}, 
  AspectRatio -> 0.75, PlotStyle -> {Black}, 
  AxesLabel -> {Style["x", 18], Style["y", 18]}, LabelStyle -> {13}, 
  PlotLegends -> {"func. 3"}]]

I would like to do the legends on the second graphs the same as on the first one. It's clear that they have different vertical shift and the line length. So, I would like to do the second legends identical to the first one if possible, of course :)

Answer 1

Use LegendMarkerSize in conjunction with a LineLegend.

Show[
 Plot[x^3, {x, 0, 3}, PlotRange -> {0, 27}, AxesOrigin -> {0, 0}, 
  AspectRatio -> 0.75, PlotStyle -> {Black, Dashed}, 
  AxesLabel -> {Style["x", 18], Style["y", 18]}, LabelStyle -> {13}, 
  PlotLegends -> 
   Placed[LineLegend[{Directive[Black, Thin, Dashed]}, {"func. 1"}, 
     LegendMarkerSize -> 20], After]]
 , Plot[x^2, {x, 0, 3}, PlotRange -> {0, 27}, AxesOrigin -> {0, 0}, 
  AspectRatio -> 0.75, PlotStyle -> {Black, Dotted}, 
  AxesLabel -> {Style["x", 18], Style["y", 18]}, LabelStyle -> {13}, 
  PlotLegends -> 
   Placed[LineLegend[{Directive[Black, Dotted]}, {"func. 2"}, 
     LegendMarkerSize -> 20], After]]
 , Plot[x, {x, 0, 3}, PlotRange -> {0, 27}, AxesOrigin -> {0, 0}, 
  AspectRatio -> 0.75, PlotStyle -> {Black, Thin}, 
  AxesLabel -> {Style["x", 18], Style["y", 18]}, LabelStyle -> {13}, 
  PlotLegends -> 
   Placed[LineLegend[{Directive[Black, Thin]}, {"func. 3"}, 
     LegendMarkerSize -> 20], After]]
 ]

I have renamed functions to ensure that the legend corresponds to the order in which the curves appear. However, a better way would be to combine plots and legends inside a Plot command and then to use the LegendLayout function as shown in 256344.

EDIT

To control the spacing: use {1, 0.7}, {1, 0.65}, {1, 0.6} as an example instead of the After in the plots, respectively.