Hi @Terebi42, thanks for your question! By answering it here I hope to help your project while also sharing answers for future users who may have the same question.

Horizontal legend

This suggestion is a good one and has been made before (#580). It is currently triaged as a moderate priority task (#1028) and I am unlikely to work on this soon. It's open for contribution though, and is on the list of possible hacktoberfest contributions #1274

How to place a legend outside the plot area

This solution is not elegant, but it works and offers a lot of flexibility. I added an item on the triage list (#1028) to hopefully make it easier to achieve this entirely within ScottPlot.

using System.Drawing;
using ScottPlot;

// render plot and legend as separate images
var plt = new Plot(400, 300);
plt.AddSignal(DataGen.Sin(51), label: "sin");
plt.AddSignal(DataGen.Cos(51), label: "cos");
Bitmap bmpPlot = plt.GetBitmap();
Bitmap bmpLegend = plt.RenderLegend();

// create a large image and place the plot and legend images onto it
Bitmap bmp = new Bitmap(bmpPlot.Width + bmpLegend.Width, bmpPlot.Height);
using Graphics gfx = Graphics.FromImage(bmp);
gfx.Clear(Color.White);
gfx.DrawImage(bmpPlot, 0, 0);
gfx.DrawImage(bmpLegend, bmpPlot.Width, (bmp.Height - bmpLegend.Height) / 2);
bmp.Save("demo.png");