As of the new Gboard Beta 15.7.3, Bitmoji may soon be deprecated and may be removed from Gboard.

New symbols keyboard on the accessory keyboard.

No flag, new option appears by default.

New Writing Tool card appearance animation in the New Gboard Beta 15.7.3.

Flag for it: enable_writing_tools_item_view_expand_anim
Value: true
Type: boolean

New education animation in Gboard Beta 15.7.3 when changing access point. The animation only appears the first time you edit access point.

Flag for it:
enable_access_points_new_education
Value: true
Type: boolean