Combine Two Legended Plots
tplot1 = Plot[PDF[NormalDistribution[], x], {x, -3, 3}, ImageSize -> 100, PlotStyle -> Directive[AbsoluteThickness[5], Gray], Filling -> Axis, FillingStyle -> LightGray, PlotLegends -> Placed[LineLegend[{"NormalDistribution"}, LabelStyle -> {Bold, Gray, 10}, LegendMarkerSize -> {15, 10}], Above]];
SeedRandom[44];
tplot2 = SmoothHistogram[RandomVariate[NormalDistribution[], 50], PlotStyle -> Directive[AbsoluteThickness[5], Orange], ImageSize -> 100, PlotLegends -> Placed[LineLegend[{"data"}, LegendMarkerSize -> {25, 10}, LabelStyle -> {Bold, Gray, 10}], Above]];plot1 = Plot[PDF[NormalDistribution[], x], {x, -3, 3}, ImageSize -> 100, PlotStyle -> Directive[AbsoluteThickness[5], Gray], Filling -> Axis, FillingStyle -> LightGray, PlotLegends -> Placed[LineLegend[{"NormalDistribution"}, LabelStyle -> {Bold, Gray, 18}, LegendMarkerSize -> {35, 10}], Above]];
SeedRandom[44];
plot2 = SmoothHistogram[RandomVariate[NormalDistribution[], 50], PlotStyle -> Directive[AbsoluteThickness[5], Orange], ImageSize -> 100, PlotLegends -> LineLegend[{"data"}, LegendMarkerSize -> {35, 10}, LabelStyle -> {Bold, Gray, 18}]];Grid[{{Show[tplot1, Ticks -> None], Show[plot1, plot2, PlotRange -> All, ImageSize -> 250]}, {Show[tplot2, Ticks -> None], SpanFromAbove}}, Frame -> All, Alignment -> {Left, Center}]