Adding a bit of a caveat to my earlier go-right-ahead:
I'm looking at manuals for mid-teens Highlanders. You don't give a model year, but since the Highlander's stated limit dropped like a rock when Toyota adopted the SAE standards and you say this one has 3,000 stated pound capacity, I'm assuming it's not a more recent unit.
Since owner's manuals cover vehicles equipped different ways:
Do be aware the Highlander's 3,000 pound upper limit applies only to those 4-cyls that have Toyota's tow package; those without are restricted to 1500 pounds. Tongue weight also enters into the equation: 300 pounds with tow package, 150 pounds without. Dunno what the "package" consists of in the Highlander's case, though it may include mods to the transmission/cooling system, trailer wiring, and sometimes a hitch or even suspension upgrades.