In Mapsource zoom out so you can see the whole track. Open the track properties. Select the first track point (or one in the middle if that is where you want to edit). You should see that point highlighted on your track. Now use the down arrow on your keyboard to scroll through the track. When you get near the point you want to edit, take note of the track point number.
Now go back to the map screen and zoom in on the area / section you want to edit. Go back to the properties tab and select the track point number noted above. Using the up or down arrows scroll to the point where you want to start your edit. Hold down the shift key and use the arrow key to select all of the track points you want to delete. The track points should be highlighted in the properties box as you select them. When you get through selecting all of the track points hit the delete key. That section of your track will be gone and the track will be continuous.
Hint: I always start / end my edit before my actual desired points. Then I zoom way in and select and delete the points a few at a time. And CTRL-Z will restore you points if you find you made a mistake. Hint 2: I always save to a different track name so I have the original file.