Hello,
GL Balances: as mentioned above......
In a trial balance list you do not have a breakdown per vendor or customer you have forgogtten assets and material... and so on 
I do not know name of such report..... seems to be a new one..... but we do not call this trial balance.
There is no report available which "shows the whole figure universe"
You can go to as an instance FBL5n - customer open item report - change layout and add GL account.
This is GL account which is in customer/vendor master.
Same for vendor open item list.
The sum at the end per GL account should be the same as in trial balance per GL account - take care of cut off date!!
GL account is also shown in balance report for customer and vendors.... here you can check if GL has the same value as sub ledger.
Run the reports mentioned, and have a close look, I am 100% sure you will find the context.
Otherwise please wirte down specification for ABAP team.......
Hope I was helpful
all the best Erwin