The new_tags.txt file lists all the new tags that have been added since the last build. It is located in the Exports folder of your project directory.
The intention is to help the user make sure that the tags get transferred to the console database, so that graphics using the tags will work. Use it as a checklist when you have to define tags by hand or export them to transfer them to the console processor.
For example, the following are new tags in a build:
15CEMENTLEVEL 16CEMENTELEVEL 16CEMENTLEVEL 1_2FLAPSTART 1_2TRAVELOVER 1_BESTA_FEEDER 1_COOLERHOTAIR 1_F_PIPE_TEMP 1_PRIMARY_AIR 1ABUNDCEAVAIL 1ABUNDCEOLOAD