Hello There,
Yes, there is a very easy way to do this. First of all when your player is connected to your computer, you can either use the Finder (Mac) or the File Explorer (Windows) to give a name to each micro-SD card. While this does not yet show up in PonoMusic World (PMW), by switching to Finder or File Explorer, you will know instantly which card is loaded.
The other way to know which card is loaded is to go to the upper left-hand corner of PMW and select "Pono Player, Drives, and Devices". This will show a list of the files loaded onto both the internal memory and the card, along with a way to tell which is which. Currently it is trivial to select tracks and then delete them by right clicking on them (I forget the equivalent for right-clicking on a Mac, but if you have a Mac you will know what to do).
At the present time, I don't believe that there is a way to move tracks from one location to another, but I fully expect that feature will be added before too long.
As far as starting a new session goes, this is not necessary at all!
Simply go to the bottom left corner of PMW and there is a box called "Action Window". If it is not open, simply click on the blue arrows in the upper right corner of the box. One of the choices will be "Sync Handheld". Click on this and you will get two new boxes, one for each memory location -- the internal memory and the micro-SD card. Again, the only indication as to which is which (at least on a Windows machine) is the drive letter, so the worst case is to switch to the Finder or File Explorer to see which drive letter corresponds to the desired memory location.
Then click on the "Music Library" selection in the upper left-hand corner of PMW and organize the music by Artist, Album, and so forth. Drag and drop the desired files into the yellow "bucket" and you should be all set to go.
Hope this helps!