Do your “red triangles” look like the illustration on this page under the heading “After locking a Play Region”? If so, you have apparently made settings that a) allow showing the timeline before time zero; b) set a Play Region; and c) locked that play region.
Deleting stuff inside /Library/Application Support/audacity is not how to reset Audacity. You need to delete the stuff inside ~/Library/Application Support/audacity. Note the “~” character at the start.
See this message for details on how to reset Audacity.
– Bill