SKAction on SKLabel with array of Strings
The first array element configText[0] is never used, so you can
remove it from the array (and modify the index calculations accordingly).
Incrementing the counter with wrap-around can be simplified using the
remainder operator:

self.counter = (self.counter + 1) % self.configText.count

The three "run" actions can be combined into one.
Inside the actions array you can refer to the SKAction members
without specifying the type explicitly, e.g. .wait instead 
of SKAction.wait.


Putting it all together:

parentNode_Label.run(
    SKAction.sequence([
        .wait(forDuration: 3.0),
        .run {
            self.sprite_Label.text = self.configText[self.counter]
            self.counter = (self.counter + 1) % self.configText.count
        },
        .fadeIn(withDuration: 0.5),
        .wait(forDuration: 3.0),
        .fadeOut(withDuration: 0.5),
        ]).forever()
)


Also have a look at the Swift naming conventions:


  Names of types and protocols are UpperCamelCase. Everything else is lowerCamelCase.


For example: parentNode, textLabel, without underscores.