@Critter_Spike, Sorry but I cannot reproduce this. The B or T Hotkeys place a via and swap the track routing to the opposite layer for me in Chromium and Firefox latest.

Thanks for responding......I'm using Firefox on my Macbook Air...I don't know how to capture the screen action to show you ...I first select the layer I wish the trace to begin on from the Layer Pallet....say for example "TopLayer" (Red) ...I then Left-Click on the first pad of the net...and begin to draw out the trace...If while I'm track-laying...I tap the "B" key....no Via is place...and the whole length of track that I've just placed essentially "flips" to the BottomLayer and turns Blue...I suppose I may be able to record a video clip to prove it...could it be related to the fact that I commenced the board design before the upgrade...I've worked round it by beginning by placing a via...then assigning it a net name to suit the trace...then routing up to the via on the top and Bottom Layers in turn...weird....I'll try it on my Windows machine and see if I get the same effect....any ideas..?

Firefox on Windows 10 machine...same issue....Incidentally I also cannot get the Copper Pour to work on either layers of my board.....

Not sure if this is related but are you creating a PCB directly or using Convert to PCB from a schematic?

You must routing the track on TopLayer, and then use the hotkey B, when you move the mouse, you will see the via.