Clarion 2 - 11.1 calls the Windows ANSI or “A” API. It is limited to 260 and will forever be limited. It is deprecated and is unlikely to be enhanced.
All this new stuff requires the Windows UNICODE or “W” API. Almost every new API in Windows since Vista only has a UNICODE prototype with no ANSI wrapper. If Clarion 12 delivers on UNICODE this will be possible but will require lots of code changes e.g. to USTRINGs for everything.