"Joint" is one of the three different "key timings" concerning the Auto Articulation of S.Art2 Voices. On Genos you can select or deselect these seperately (in "Voice Setting" display).
Quote from Genos Reference Manual, page 41:
Voice Setting
> S.Art2/Arpeggio
> S.Art2 Auto Articulation
Determines whether articulation is added to S.Art2 Voices automatically for these respective key timings:
• Head: When the first key is pressed.
• Joint: When the key is pressed or released while holding down other key(s).
• Tail: When the last key is released.
Unfortunately, the user cannot edit anything regarding the individual articulations of S.Art2 Voices.
Best regards,
Chris