It is annoying that TheTVDB implemented Specials as part of Season 0. It would have been better if they implemented x.y terminology from the start so that Episodes went 9, 9.1, 9.2, 10, etc., where all the Episodes with decimals are non-core Episodes, such as Specials. But they didn't, so we have to live with it.
Unfortunately, both of Brian's method will result in trouble if, by any chance, you run the "Get Movie & TV Info..." against any of these Episodes with non-standard episode numbers. For that very reason, I implemented a policy of always using the Episode numbering structure of TheTVDB a long time ago, even when it was a pain.
The good news is that it is easy to sort all Episodes and specials in chronological first aired date. Most of the time this date is accurate, although some studios/broadcasters have shown Episodes out of the sequence intended by the producers, and that can muck things up.
Doctor Who is easy though, as an example. Just sort your View of the [Series] by [Date], which is the Originally Aired date from TheTVDB, and Specials will be sorted correctly, interspersed among the core Episodes.
In Standard View you could change the sort for the existing TV Shows View, although it is probably better to create a specific View for this issue. The list display shows what you want clearly.
In Theatre View it would be best to create a new View that adds a sort by [Date] at the "Set rules for file display" level, and does not include the [Season] sort in the Details section of the View. The first two attached images show the setup, and the last the result. Yes, it is just a big list of Episodes, but it does sort the way you want.