I think it is necessary to create two checklist entries.
1st entry:
Source: ^. -ABC
Target: ABC
Search mode: Regular Expressions
PowerSearch: On.
This entry will find all segments that contain ABC in target but is missing in source and highlight ABC in target and the 1st character in source.
2nd entry:
Source: ABC
Target: ABC
Search mode: Simple
PowerSearch: On.
This entry will find all segments that contain ABC in source and target. It will also highlight only ABC in source and target.
Regards,
Oscar.