Merge Action History from 2 workflow messaage

Hi, We have approval requirement to show different Approval Action based on Approver type. So we created 2 different notificaitons and based on the Approver type send the appropriate notification. Now we would like to show the combined Action History in the 2 approval notifications.

We can create a custom Approval reqion and set it to message attribute #HISTORY.

Question: How do I get the content of the Action History from the 2 approval notificaitons?

Any example or white papper availble for the above scenario?