Sorry about the delay in responding. I missed the fact that you posted another question.
After going through the first review process, the idea of using the 7th transcriber-defined indicator was shot down. It was deemed that assigning a specific meaning to one of the transcriber-defined indicators was not a good idea. The ICEB code maintenance committee (the "owners" of UEB) have been asked to create a base reference indicator. In the meantime, what to do with marginal labels?
We are proposing that a key be created for the labels themselves using the UEB icon concept (dot 4, dots 1246 before letters representing the key). Then use the braille grouping indicators (dots 126, 345 from section 3.4) to surround the text that the label applies to. You will likely need grade 1 indicators preceding the braille grouping indicators. Again, this is PROPOSED and must still go through another review. Of course, the symbols must all be explained in a TN before the text.