Paulus, see this post that I just created with a list of supported FLEx markers. I guess you can choose from that list any marker that comes more or less close to what you are looking for. For my liking there is a lot that DAB does not support, but there is always a workaround.
With custom numbering, I am pretty sure this is not possible with LIFT, I don’t know if XHTML can do it. Converting a Toolbox dictionary to FLEx should be simple.