The JTX_Transactions table is a legacy table that is not created with Workflow Manager Classic, versions 10.3 and later. It sounds like you are starting with a new implementation of 10.8.1 so that explains why you would not see it.
If you haven't seen it already, we do include a database design document with each install of Classic Desktop. By default, it is located at C:\Program Files (x86)\ArcGIS\WMX\Desktop<VERSIONNUMBER>\Help
Let me know if you have any further questions.