we do have a dedicated transaction DIASBU to transfer only diaries from one user to another user.
Enter the old user ID and you could see count of diaries to be transferred will get updated
automatically once the old user ID is entered. Now, you can enter the new user ID to whom all
the diaries need to be transferred.
You can run the test after entering the details and check log for any warnings or errors.
If there are no warning or errors, you can click on process icon to complete the transfer
from one user to another user.