Thanks @jetdv for the guidance. I managed to get something banged out.

The script works perfectly in VP13.

As you mentioned - "Change "Using ScriptPortal.Vegas" to "Using Sony.Vegas" for version 13." - Changing it to Using ScriptPortal.Vegas should make this work in the more recent Magix versions of VP.

Here is the working script , with instructions :
 

1. Open a text editor - Notepad or Notepad++ will be good enough.
2. Create a new file and copy the script code into it.
3. Save the file with a .cs extension, such as vegas_add_media_from_list.cs.
4. Open Vegas Pro and ensure that the project you want to work with is open or create a new project.
5. Run the script by going to the "Tools" menu in Vegas Pro and selecting "Scripting" and then "Run Script...". Browse and select the script file from the file dialog.
6. A file selection dialog will open. Browse and select the folder that contains the 'list.txt' file.
7. The script will read the 'list.txt' file, locate the media files listed in it, and insert them into the Vegas Pro timeline in the same order specified in the file.
8. Once the script execution is complete, you will see the media files inserted into the timeline without any gaps between them.

The list.txt file should look like this:

C:\Users\Documents\source videos\e1a.MP4
C:\Users\Documents\source videos\e1b.MP4
C:\Users\Documents\source videos\english (2).JPG
C:\Users\Documents\source videos\e2a.MP4
C:\Users\Documents\source videos\e2b.MP4
C:\Users\Documents\source videos\english (3).JPG
C:\Users\Documents\source videos\english (4).JPG
C:\Users\Documents\source videos\e3.MP4
C:\Users\Documents\source videos\e4.MP4
C:\Users\Documents\source videos\e5.MP4

This is the script :
Change using ScriptPortal.Vegas; to Using Sony.Vegas" for version 13. No change required for Magix versions of VP.

using System;
using System.IO;
using System.Windows.Forms;
using ScriptPortal.Vegas;

namespace SampleScript1
{
    public class EntryPoint
    {
        public void FromVegas(Vegas vegas)
        {
            // Open a dialog box to select a folder
            string selectedFolder = SelectFolder();
            if (selectedFolder == null)
            {
                MessageBox.Show("No folder selected.");
                return;
            }

            // Find the 'list.txt' file in the selected folder
            string listFilePath = Path.Combine(selectedFolder, "list.txt");
            if (!File.Exists(listFilePath))
            {
                MessageBox.Show("Could not find 'list.txt' in the selected folder.");
                return;
            }

            // Read the file and extract the media file paths
            string[] lines = File.ReadAllLines(listFilePath);
            string[] mediaFiles = Array.FindAll(lines, line => IsMediaFile(line));

            // Insert the media files into the timeline
            int trackIndex = 0; // Target track index
            Timecode cursorPosition = vegas.Transport.CursorPosition;
            foreach (string mediaFile in mediaFiles)
            {
                InsertFileAt(vegas, mediaFile, trackIndex, cursorPosition);
                TrackEvent lastEvent = GetLastEvent(vegas.Project.Tracks[trackIndex]);
                cursorPosition = lastEvent.End;
            }

            MessageBox.Show("Media files inserted successfully.");
        }

        private string SelectFolder()
        {
            using (var dialog = new FolderBrowserDialog())
            {
                dialog.Description = "Select a folder";
                dialog.ShowNewFolderButton = false;

                if (dialog.ShowDialog() == DialogResult.OK)
                {
                    return dialog.SelectedPath;
                }
            }
            return null;
        }

        private bool IsMediaFile(string filePath)
        {
            string extension = Path.GetExtension(filePath).ToLower();
            return extension == ".mp4" || extension == ".mov" || extension == ".avi" || extension == ".jpeg" || extension == ".jpg" || extension == ".png";
        }

        private void InsertFileAt(Vegas vegas, string fileName, int trackIndex, Timecode cursorPosition)
        {
            foreach (Track track in vegas.Project.Tracks)
            {
                track.Selected = false;
            }
            vegas.Project.Tracks[trackIndex].Selected = true;
            vegas.Transport.CursorPosition = cursorPosition;
            vegas.OpenFile(fileName);
        }

        private TrackEvent GetLastEvent(Track track)
        {
            TrackEvent lastEvent = null;
            foreach (TrackEvent trackEvent in track.Events)
            {
                if (lastEvent == null || trackEvent.End > lastEvent.End)
                {
                    lastEvent = trackEvent;
                }
            }
            return lastEvent;
        }
    }
}

* Credit goes to @jetdv for providing the guidance and the documentation for getting this done.