You will have a loop, for example with say 3 straight line sections where Memory Map has chosen to join your walks, at the points where the GPS was switched off then back on again.
When you have the route uploaded onto the PC back home, right click at one end of a straight line and choose SPLIT TRACK from the drop down menu. Do the same at the other end of the line.
Right click on the now separated straight line and choose delete.
Do this for all unwanted sections.
When you split a section of track, Memory Map names it as a split portion of the original track.
Right click on a track or newly split section and go to properties to re-name or change the colour etc of any track sections you create.
If you end up with an unwanted waypoint or two on a route, then right click on the part of the track you want to simplify and choose REMOVE TRACKPOINT.
You can’t undo with Memory Map as in MS WORD etc so before you mess with your overlay, save a copy of the current one by clicking OVERLAY / EXPORT ALL and save the backup mmo file in a folder in My Docs or whatever. Save as many overlays as you like and double click on them to open them up in Memory Map at a later time or import them.