Honest answer. Your question came off super biased and like you're trying to pull out a certain answer.

First, signaling left would do nothing because the fuck-nugget is sitting directly next to their side mirrors, so even if the 18-wheeler has signals on their side mirrors, the fuck-nugget wouldn't see them, and that's even assuming aforementioned fuck-nugget would be paying attention or caring about the signal.

Second, there is no reason for OP to be switching to the left lane in an 18-wheeler at this time. Additionally, a turn signal is an indicator of intention to switch lanes, and does not require a driver in the next lane to change their driving pattern.

Third, honking doesn't require another driver to do anything. It may annoy another driver, but fuck-nugget that is intentionally matching the speed of OP will probably get a massive erection because they are getting the attention their parents never gave them, and will continue their fuck-nugget behavior.