In older Premiere versions the forward/backward Track Select Tool (shortcut 'A') by default was selecting one track, and with Shift it was selecting all tracks (I don't remember if there was an option to select multiple tracks).
Why on earth have Premiere people decided to reverse this intuitive and simple behaviour to something opposite and absolutely counterproductive is beyond me... Now when I select the 'A' tool it by default selects all tracks. So if I want to select one track, I need to press Shift, then grab the track, then release Shift, and only then I am able to move it. So many unnecessary actions that take a lot of time and finger coordination to do a simple thing. In all the software that I know SHIFT is by default used to select multiple items, and it makes sense. Actually even in Premiere all the other tools with Shift allow selecting multiple items, except the 'A' tool.
I wish this could be fixed and also a Multiple track selection option added. To please all users, this could be an option of choice if needed.
I think you are mistaken.
A is default all tracks and shift will give one track: always been like that.
hmmm, nope. in older versions (I cannot tell which, but probably a few years back) 'A' was for single layer.
That was a long time ago. Version CC 2015.
But it became very obvious and frustrating to me now, probably because I didn't have a need to use this tool so often.