The phrase "whole subplot" refers to a smaller, complete story that is part of a larger main story. It has its own characters, events, and development, but is connected to the main storyline. Full definition
There were whole subplots which could have been pared down, and I got rather tired of the main character's personal life. (madgeniusclub.com)
While the latter pair offer some laughs at the extent of their creepiness (If a style of dancing could be classified as that of a serial, it would be Donny's), it's unfortunate that the whole subplot brings the whole film to a standard, extended, and poorly paced chase sequence. (markreviewsmovies.com)
There's a whole subplot about a Vietnamese priest that purposefully refuses to make any kind of sense for most of the run time. (screenpicks.com)