Using Kolibri version 0.10
As per step 11 at https://kolibri.readthedocs.io/en/latest/manage.html#import-content-from-kolibri-studio, to update an already imported channel one must use “Import more”. Thereafter there is an option to Update channel version. Hitting that shows “Channel up-to-date” but thereafter it requires reimporting the entire set of contents for that channel instead of just fetching/syncing the updates only.
The channel had vanished from the Channels list on my device until I re-downloaded the entire channel again.
Is this the desired behaviour? I guess not as I had to re-download around 167 GB of Khan Academy content. I tried this process with Khan Academy (Hindi) as well to be sure that I had not made any mistake and there too I had to re-download around 1 GB which seems like the entire set.