NOTE: The following steps can only be performed on a Windows computer. The copy and paste option does not function in the track properties window on a Mac computer.
Making a Duplicate Track
First, it is a good idea to make a duplicate of the initial track you want to join the other tracks into. This ensures your original is intact if you decide you do not like the final result, or you need it for other purposes.
Select a track from the left panel (done by clicking the track name).
Select Edit from the top toolbar.
Select Duplicate.
This creates a duplicate of the initial track with a name that combines the original name and a generic numeric name, like Original Name Track 001. While editing, it can help to rename a track so it is easier to find, or change its color to differentiate it from other tracks. For steps, see - Editing Track Properties - Windows.
Copy and Paste Track Points From Secondary Tracks
Next, copy the track points from any secondary tracks and paste them into the initial track.
Double-click the track to copy points from. This opens a Track Properties window.
Highlight the listed track points.
To highlight all track points, right-click in the list and choose Select All.
To highlight a range of track points, select one track point, hold Shift on your keyboard, and select another another track point. All track points between the two will be highlighted.
Right-click the highlighted section and select Copy.
Close the window.
Double-click the initial duplicate track.
Right-click in the track point list and select Paste.
The pasted track points should now be at the bottom of the list. Repeat steps 1-6 for any additional tracks points you want to add to the initial duplicate track.