Hi Renatas,
I came to an end that I used a BADI to pick up the GL account from customer master instead of GL account in configuration. The reason is I also want to post to a vendor account in some cases, so I had to use the enhancement. It helped to get the recon account in customer as well. I tested and got successful with ABAP support.
Thanks for all your information that made me clear on this part. I still have some issues open in Treasury and Loans Management. I may open some more discussions. Hope to have a chance of sharing knowledge and experience.
Have a nice weekend!
Thanks and Regards,
Yen Ngo