Initially I thought it was simply another error with Microsoft's dictionary including the American spelling and not the Australian spelling for a word. But this time it turns out to be a little more complicated.
The spelling shoveller does need to be included and will be. A shoveller is someone who shovels, such as a person who shovels snow.
Normally in the situation of an American spelling the result is the single 'l' version of the word is removed, but not in this case. It turns out that shoveler is a type of bird found in America and Eurasia.
I did found one reference in Wikipedia, The shovelers, formerly known as shovellers, are four species of dabbling ducks with long, broad spatula-shaped beak", so it does appear there has also been a change in the British spelling as well. However Wikipedia isn't a good authoritative reference for Australians as I've found many errors over time and Wikipedia doesn't make it easy to identify the preferred Australian English spelling.
The Oxford online (British dictionary) shows the following under origin.
late Middle English (denoting a spoonbill): alteration of earlier shovelard, from shovel, perhaps influenced by mallard
I then used Google UK and limited pages to UK sites. The spelling usage for shoveler duck when compared to shoveller duck is two to one. This supports the greater use of shoveler duck as the preferred spelling in the UK and also for Australians. I did this test to reduce the effect of American spelling on search results.
In summary, both shoveller and shoveler need to be included in the Australian dictionary, but it is important to note the spelling with the single 'l' refers to a duck.