Adding of users to multiple organisations as administrators

Hi all

me facing a issue when try to add user created at site level and add the same user to different organisations as creators ( for product/project/.. and also as administrators for organisations ) and below is the scenario .

Under Site I have created multiple organisations say A,B,C . I have created some users at site level without defining organisation for the the users while creating the user .

when i try to add this users to all three organisations as creators/administrators search results will show only users related to particular organisation defineed while creating the users but not the users created at site level without organisation.

Can anyone assist me how to add users without organisation defined to differnt organisations as creators or administrators.

Thanks in advance