1. Manually assign a glAccount to an organization (Accounting->Global GL Settings->Chart Of Accounts->Assign Gl Account or Accounting->Organization GL Settings->Setup->Chart of Accounts)
2. Perform operations that create transactions for the organizations glAccount
3. Run the Accounting->Organization GL Settings->Accounting->Reports->Trial Balance
Notice that the glAccountId assigned in step 1 is not listed in the results. This is due to TrialBalance.groovy applying a fromDate filter to GlAccountOrganizationAndClass which is not set in step 1. Updating glAccountOrganization fromDate to something within the trial balance range resolves the problem.