If you don't use the fonts from the warning message in Finale at all, just ignore the warning message and select yes.
If you
only use the font files in other notation software (e.g. Capella, Sibelius), ignore the warning message too.
If you have never used these fonts before in Finale, but wish to use them now or later, just ignore the warning message.
In other words the warning message is
only relevant, if you have
already used the mentioned fonts in older Finale documents, because when re-opening these documents it is possible that Finale displays wrong symbols if the MacSymbolFonts.txt entry has changed.
But it is a
reversible process: if you select yes the MacSymbolFonts.txt will be automatically updated. Should you encounter any symbol problems later in older documents that use these fonts, you can simply remove the added font name manually from MacSymbolsFonts.txt later.
Finale®'s MacSymbolFonts.txt file includes a list of music fonts for Finale's internal font handling. The program uses a different font encoding when a font is on the list. Fonts can have several encodings. This means for example if you select the character 138, a different symbol appears if the font is in MacSymbolFonts.txt or if not.
Very often fonts have several encodings (e.g. for MacOS and for Windows) and not all of them fully work in Finale® (on MacOS and/or on Windows), so one has to test which encoding works best.
This also depends on how you work, what fonts you use and what you need:
While Windows is more tolerant regarding the selected encoding, MacOS very often requires the font name to be added to MacSymbolFonts.txt.
So if a Finale® document is to be exchanged between MacOS and Windows, it is recommended to have matching MacSymbolFonts.txt files.
Note:
Unicode fonts (=fonts with more than 255 symbols like Aruvarb or November2) must never be added to MacSymbolFonts.txt, as MacSymbolFonts.txt automatically limits the number of available symbols top 256.
The Perfect Layout plug-in currently only supports one type of encoding for each music font. That's why you will get an error message if MacSymbolFonts.txt doesn't match the encoding that the plug-in requires.
The plug-in will automatically update MacSymbolFonts.txt if it is not compatible. After the update a restart of Finale is necessary.
When the MacOS version of the Perfect Layout plug-in is released, the recommended font encodings might slightly change to guarantee best compatibility between MacOS and Windows.
In general it is save to just follow the suggestions of the Perfect Layout plug-in regarding MacSymbolFonts.txt.
But
attention must be paid if you have manually adjusted font annotation files that don't mark the glyph borders, but have user-defined borders that don't match the glyph borders (for whatever reason ... usually this is not recommended and not necessary):
these font annotation files are not compatible with a changed encoding and need to be recreated.