There are a few rules what we can combine. Obviously, we cannot write:

procedure Test; abstract;
begin
end;

we can only have something like this:

type
  TMyClass = class
  public
    procedure Test; virtual; abstract;
  end;

So an abstract can only appear after a virtual and the virtual (and override) can only appear for methods. Same for "reintroduce", "overload" and more. There are rather complex rules which are not modelled by this representation. For a syntax highlighter this might not be a problem, but it might, if someone wants to use it for more.