If what's needed is to redefine the default glyph generated by the FM markup "\b", I'm not aware of any way to do that.
But it's simple to edit Paragraph Formats for any bulleted forms, and specify what glyph to use. On FM8 or higher, I would avoid using the old codepage font method, and instead use Unicode. Either choose a body font that populates the codepoint for the glyph you want, or invoke one that does, just for the bullet (Arial Unicode MS if necessary).
In Format > Paragraph > Designer for the bulleted form, it's the Numbering tab. The most obvious markup would be:
\u25e6\t
Which is the Unicode WHITE BULLET and a tab.
Other candidate glyphs might include:
\u25e6
\u25cb
\u25ef
\u274d
\u29bf
\u2299
\u229a
\u233e
\u2a00
\uffee
or even a non-breaking space and combining circle:
\ \u20dd
If your preferred body font doesn't populate the desired bullet code point, create a Character Format, named perhaps "Bullets", that is As-Is or blank for everything except Font Family, which would select a typeface that does populate the codepoints of interest. Then select that Character Format in the Paragraph Designer menu for your bulleted para formats.
