Appender Code

using System;
using System.IO;
using log4net.Appender;
using log4net.Core;
using UnityEngine;

public class UnityDebugAppender : AppenderSkeleton
{
    protected override void Append(LoggingEvent loggingEvent)
    {

        var fileName = loggingEvent.LocationInformation.FileName;
        var path = GetRelativePath(fileName, "D:/Windows/Documents/Unity/Prehistorik Era");
        var message = RenderLoggingEvent(loggingEvent);
        Debug.Log($"{message} (at {path}:)");
    }

    string GetRelativePath(string filespec, string folder)
    {
        Uri pathUri = new Uri(filespec);
        // Folders must end in a slash
        if (!folder.EndsWith(Path.DirectorySeparatorChar.ToString()))
        {
            folder += Path.DirectorySeparatorChar;
        }
        Uri folderUri = new Uri(folder);
        return Uri.UnescapeDataString(folderUri.MakeRelativeUri(pathUri).ToString());
//        return Uri.UnescapeDataString(folderUri.MakeRelativeUri(pathUri).ToString().Replace('/', Path.DirectorySeparatorChar));
    }
}a