Simplify nested if/else with repeated results?

You could check with the result of the first check.

This is an exclusive OR check.

// typeof inverse === 'boolean'

function handleDirection(src) {
    if (src === 'left' === inverse) {
        tracker--;
    } else {
        tracker++;
    }
}

The check evaluates the expression in this order (src === 'left') === inverse:

src === 'left' === inverse
---- first ---             returns a boolean value
--------- second --------- take result of former check & compairs it with another boolean