Current (Shift+)Tab (De-)indents a list item, but in any other context it falls back to native behaviour and ends up blurring the whole document. If the user expects Tab to perform a document action it's a bit annoying if the end up leaving the document, so we should either have it do something (next paragraph?) or prevent default.
In table cells Tab should move to the next cell (as in Google Docs, LOffice etc.) fixed