Thanks for your question - for those who can't access the pdf, the question is regarding transcribing IPA as a language in an Italian vocal piece, specifically about using the quotation marks to show the merged syllables.
The transcription you've begun looks good so far. On line 2 of the example you sent, the closing merger quotation mark should come after the l in "il" since it's all one syllable.
There could potentially be a problem using the quotation marks to show the merged syllables, since IPA uses dots 236 in combination with other letters for specific symbols. (hooktop h, curly-tail j, and others.) If you can go through the entire volume/project/piece and determine that you don't have to use dots 236 for any IPA symbol, I think you're good to go with using those dots for merged syllables. (The same applies, of course, to dots 356.) If you find you have to use those dots for the IPA symbols, we'll have to think of something else to do for the merged syllables.
Let me know if you need to figure something out with the merged syllables!