Hello
Sorry for late reply, hope it is still useful.
If the GPX had one track segment per day, you would get what you expect: each day would be displayed as a different segment, disconnected from the others.
It looks like your Garmin in mixing all days in a single segment, which is surprising as you are stopping and restarting recording.
Could you share a sample multi-days GPX so that we can check this?
Could it be that your GPS device has an option to create a new segment when you restart? You should look at this.
WTracks offers no option to split automatically. You can however manually split, let me know if you have trouble with this.
Thanks for your feedback
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Olivier