Works in 4.0.7 GAL canvas. I can place the via even by normal left click. (By the way track mode is shortcut X for me. T brings up the search tool.)
Is it possible that something is too close to the location where you want to place the via? (DRC might not allow it to be placed there.)
To make sure this is not the case test this where no other traces are close.
My workflow: switch to track tool, left click at the end of one of the traces, press v, left click again at the same place (It does snap to the end of the trace). -> via is placed as expected.
I can also place a via this way in the middle of a trace. (Here it snaps to the intersection of a grid line and the trace on which i want to place my via.)
If it does not work in nightly any more, then this is a regression. (Make a bug report.)