Number of supported screens on MacBook Pro I have a Mid-2018 Mac Book Pro.

On its 2nd Display Support Option it writes the following


  *In addition to simultaneous support of the internal display, this model supports a single external display up to 5120x2880 at 60Hz at
  over a billion color, up to two displays up to 4096x2304 at 60Hz at
  millions of colors, or up to two displays up to 3840x2160 at 60Hz at
  over a billion colors via Thunderbolt 3 (USB-C).


I cannot infer however from the above, whether the particular MacBook can support:


  3 external displays with resolution 2560 x 1440


Any interpretations on this?
I'd say that your MBP is limited to 2 external monitors. You can't sub-divide the same number of pixels across more displays.