I'd like to be able to double-click on the columns ,e.g. torrent name to sort alphabetically and choose ascending or descending, but Tixati won't let me do it.

on the transfers tab press the layout button.
make sure 'Sortable View' is selected

That option isn't shown. Version 2.83

it's there.

https://support.tixati.com/transfers%20view

Thanks. I was right-clicking on the 'Transfers' button, which does have a 'Layout' option, but doesn't include the sortable view option. Once I pressed the separate 'Layout' button on the right-hand side of the screen, that option was available.  Bit confusing.