Washington state has a top-two system. In top-two systems, no minor party candidate ever qualifies for the November ballot unless there is only one major party candidate in the primary, in that same race.
In November 2016, ten Libertarians appeared on the ballot for state legislature, because they all filed in districts with only one major party candidate. For 2018, there will be only four such legislative races. The four lucky Libertarians who will automatically place second in the August primary, and thus appear on the November ballot, are: State Senate 36 Bryan Simonson; Representative 22(2) Allan Acosta; Representative 36(1) Sydney Wissel; and Representative 36(2) Matt Dubin.
No other Washington minor parties had any candidates on the November 2016 ballot (except for President), and no others will have one on the November 2018 ballot.