For what it is worth, personally, I would be tempted to use UEB's composite symbol for horizontal juxtaposition (GTM §14.3.4) but would probably not use it, trusting the braille user to recognize the significance of two sequential equals symbols without my grubby little transcriber hands getting into the content.
14.3.4 Horizontal Juxtaposition ;=
"Horizontal juxtaposition" is to be invoked only when two symbols are written in close proximity and it is clear from the usage that a new single symbol, distinct from the elementary symbols considered in sequence, is intended. Otherwise, symbols written one after the other should simply be brailled accordingly.
If you had an example to share, Shellee, I would love that because the committee could come to a decision for that specific circumstance.
–Kyle