sorry to have to ask again...
The prior dialog got me to where I can build for either AVR or Teensy3.1 with the same project file and source. I just choose the desired target MCU and serial port.  I was able to remove the -Defines from the project settings and put them in the Teensy boards.txt (like the CPU speed). This done, I can compile for the AVR or Teensy 3.1.

On to the problem. When I choose Teensy 3.0 as the target, I get the numerous errors as happened originally when the -D's were not in the project file. The boards.txt file for both Teensy 3.0 and 3.1 have the same added build options 5,6,7 to eliminate need for them in the project properties. I just can't get a build for 3.0 to work as does 3.1 or AVR.

If, when choosing Teensy 3.0 I put the -D's back in the project -D's as was originally done, then it compiles. I exit and restart VS/CM of course.

Stumped.
I feel like a blind man at a NASCAR race - just don't understand this complex house of cards IDE. But then, when I did a big project with Eclipse it was much worse!

I apologize.. my "bad". I thought I had deleted that post, above. the problem was simply that the boards.txt file was edited wrong by me. I had copy/paste from Teensy 3.1 but it should have been done with removal of the ".1" for Teensy 3.0.

It's working perfectly now, toggling between T3.0, T3.1, AVR with just a choice of target. No changes to project properties, no need for new additions to the Debug/Release folder. I love it!