Your research has served you well. The real issue is an on-the-spot determination by the police officer, who will decide whether you were acting "furtively" with the "intent to conceal" a weapon. While those terms have legal definitions, an arresting officer will have a far more practical evaluation process -- "is this guy up to no good?"
The concealed carry laws in Washington State (and many other states) only allow you to carry a concealed _pistol_ and not any other form of weapon. Going through the process and getting a concealed weapon permit would certainly help in a defense, but it is not a complete defense to a charge of carrying a concealed bladed weapon nor is it any guarantee of not being arrested for carrying a concealed knife.
Vancouver has a municipal code section on point, Vanc. Muni. Code § 7.11.020(a), which reads, "It is unlawful for anyone knowingly to carry concealed on one's person any dangerous knife."
I guess the real question you pose is, "would a guy with a 7" folding-blade knife be up to no good?" Only you can answer that question before a police offer answers it for you.