MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4
The optimizer_trace system variable has these on/off switches:
          enabled: Enables (ON) or
          disables (OFF) tracing
        
          one_line: If set to ON,
          the trace contains no whitespace, thus conserving space. This
          renders the trace difficult to read for humans, still usable
          by JSON parsers, since they ignore whitespace.