I have conventions for note titles, tags and notebook names that leverages column sorting in List View. I am finding a very significant change in sort behavior I think starting with this release (also I checked that this new change is still present in 6.13 beta, so no clear immediate hope for a fix). Specific example: click once on Title column header to obtain Title sort (either ascending or descending). Click next on Tags header and all sorting, indicated and actual, vanishes (or is replaced with some indiscernible sort, and no arrowed column header). Click Tags header again and obtain tags sorting, however, secondary sorting on Title is now lost. The old behavior was very desirable and useful, that is that in this example, the title sort would have been preserved as a secondary sort key, evident in ranges of equal primary key (here Tags). I think I recall from an old CS course that this property of sorting is called stability, hence my subject line.
So really there are two problems here in my opinion, likely related, the stability that used to allow secondary sorting is gone, and that clicking a second column has first the action of removing all sorting. If this is a feature, I'm missing how so. Seeing this on macOS 10.13 and macOS 10.12.6.
Update: I've been messing with this more and the problem seems to only afflict Notebook and Tags columns, both the problem that the first click on that column sends the whole view into an unsorted state (and with no sort arrow showing anywhere), and also the loss of stability, i.e., secondary key sort. I think it's reasonable to expect that Title sort would be preserved for equal Notebooks in list view, as it used to be. I'm surprised nobody else seems to care about this... anyone??