When you give a unique name to each track, it changes the name of the audio files that are created in your recording folder. So, instead of "Audio Track7.wav," it might be called "Rhythm Idea7.wav."
If you want to change the track names of the files you mix down, you can edit the track markers and enter the names in the Title box. Note: every Mixcraft project has a track marker all the way to the left. Add a title to that one for track 1.
When you go to mix down, there is a "Use Marker Title" option to select. Also, click on the Tag Info button to add any ID3 tags you want in your audio file.
But looking at this, you helped me find a bug in Mixcraft 6.1 build 204. The "Use Marker Titles" option is grayed out unless I select "Mix Each Track To A Separate Track" and then un-select it. I will file a bug report on this problem. What version and build of Mixcraft are you using?