+++ This bug was initially created as a clone of T33255: jquery.tablesorter should support sorting by multiple columns +++
In any sortable table, you can sort based on multiple columns by sorting by one first, then holding Shift and clicking on more. You can play with it on any table, for example the one in https://en.wikipedia.org/wiki/List_of_sovereign_states
However, this is not discoverable at all if you don't know about it; there isn't even a tooltip or anything. This should be changed, but I don't know how to design this, so I'm creating this bug.