Reply To: Need help identifying accent symbol
As you say this English, and because we can say that the symbols are not currently included in the UEB symbol set, a transcriber-defined symbol (Rules of UEB 3.26) will perhaps be the most economical way of representing this.
The transcriber-defined symbol should be included in the SPECIAL SYMBOLS list if it is used frequently in the materials you are transcribing. If it is used only a few times, a transcriber's note placed immediately preceding its use in text will be appropriate. Follow 3.2.2 in Braille Formats if the latter type of transcriber's note is used.
All of the above considered, because the symbol is found in a pronunciation key in the book, it is also possible that what you have encountered is a particular way of representing the "top tie bar" in the international phonetic alphabet (IPA). The IPA symbol for the top tie bar across two letters is a dot 5 placed unspaced between the tied letters. Its use is displayed on page 22 of the IPA guidebook: https://iceb.org/IPA-braille_print-ed_final.pdf
You may also want to check with the UEB Skills Group for other options.
We hope this helps!