how I can turn off the automatic track width feature in KiCad 6.0?
I have created some manual track with in the list. But when using them KiCad always change it according one already connected track. So one smaller track is already connected to a TH pad, then I want to add a larger one, even selected manually the larger tack with, KiCad will route wit the smaller one.
A better way is probably to set up net classes in: PCB Editor / File / Board Setup / Design Rules / Net Classes With net classes you can make a group of nets and assign track properties (width, clearance, via sizes, etc) to them.
In theory yes but there are still use cases where you want to set a different width then in the net class. e.g. when you need a smaller wire size then normal to get between two pads or to fit more wires into the same part of the PCB. Another example would be power lines: you normally don’t need a 1mm wide power line for every IC (for most you probably can’t use this size at all) but if you board draws enough power you probably need it on your main power connection, DCDC, LDO or whatever.