Version 12.0 included an embedded workflow indicator (bookmark type fold in upper right of a workflow monitor), this no longer exists in 12.3:
Created Workflow.
Add a second workflow within the workflow.
Run workflow.
Click Last Monitor
In the workflow monitor, there is no Embedded Workflow indicator to click on.
Double clicking on workflow expands it instead.
Release : 12.3
Component : AUTOMIC WEB INTERFACE
In 12.3, Double clicking on workflow expands it instead.
There are currently no plans to re-introduce the Embedded Workflow indicator as the change has been identified to be too large for a bugfix.
If the re-introduction of this feature interests you, please file an enhancement request.