Is there a way to change the order of accounts in the toolbar?

@mackim Unfortunately, there is no way for users to configure the account order or groupings in the left sidebar. 

But the developers are planning changes. If you visit this Idea thread, you'll see in the blue box under the first post that voting has been disabled because the request has been marked "Planned." Only a small number of Idea threads get coded as Planned or Under Consideration; even more unusually, there's a note there: "We are currently investigating account list customization options, however, these options may be more like enabling custom groupings rather than an alphabetical ‘sort’." So the answer to your question is no -- for now -- with a promise that some customizability is forthcoming in a future release.