Clean water tank only clean water or add detergent as well?

I am seeing mixed posts and comments what’s the recommended way of this? As we have detergent bottle in the dock so I assume we don’t have to mix it as robot will mix automatically but in the user guide it says to mix. I am little confused. As online it says if we mix it might clog or streak

You can add solution to the clean-water tank, but only if it’s the officially-approved cleaning solution and you follow the dilution ratio shown on the bottle (the manual explicitly allows approved solution in the clean-water tank and warns against other liquids).  

Important: don’t do both at once (tank + dispenser), or you risk over-concentrating the mix.

I let mine mix it itself and it smells quite nice when mopping

You do need both. Mix in tank is for floor cleaning. It helps. In the tank this is purely for mop cleaning.  Not for the floor