It looks like MuseScore generates different XML for a chord depending on how I enter the chord, and BIAB interprets the chords differently when importing.

When I enter CMaj7 and Dmi7 in MuseScore, BIAB displays the chords as expected. When I use MuseScore shortcuts Ct7 and D-7, BIAB displays C7 and D7.

Details:
It looks like BIAB is not interpreting the use-symbols attribute of the <kind> element when importing MusicXML in certain cases.

Here’s how I entered the chords in MuseScore:
Measure 1: CMaj7
Measure 2: Ct7
Measure 3: Dmi7
Measure 4: D-7

Here's the relevant XML for the first measure (entered in MuseScore as CMaj7, displayed as expected in BIAB):
Code:
  <harmony print-frame="no">
    <root>
      <root-step>C</root-step>
    </root>
    <kind text="Maj7">major-seventh</kind>
  </harmony>

Here's the relevant XML for the second measure (entered in MuseScore as Ct7, displayed as C7 in BIAB):
Code:
  <harmony print-frame="no">
    <root>
      <root-step>C</root-step>
    </root>
    <kind text="7" use-symbols="yes">major-seventh</kind>
  </harmony>

Here's the relevant XML for the third measure (entered in MuseScore as Dmi7, displayed as expected in BIAB):
Code:
  <harmony print-frame="no">
    <root>
      <root-step>D</root-step>
    </root>
    <kind text="mi7">minor-seventh</kind>
  </harmony>

Here's the relevant XML for the fourth measure (entered in MuseScore as D-7, displayed as D7 in BIAB):
Code:
  <harmony print-frame="no">
    <root>
      <root-step>D</root-step>
    </root>
    <kind text="7" use-symbols="yes">minor-seventh</kind>
  </harmony>

Exported from MuseScore as uncompressed MusicXML (results are the same with compressed MusicXML).
Imported into BIAB.

Results displayed in BIAB:
Measure 1: C[triangle]7
Measure 2: C7
Measure 3: D-7
Measure 4: D7

I didn't test the other MuseScore shortcuts for major and minor chords. Diminished, half-diminished, and augmented chords came through as expected.

I hope this helps,
-Robert