Page sequence stacks; among the enhancements to page sequence controls in version 10 came ‘psequp’ and ‘pseqdown’.
No as well as being able to control the sequence via control stream and in-line on a single level you can now also ‘stack’ sequences i.e. controlling them in-line turning on nested page sequences in turn with psequp and switching back to the previous sequence down the stack with pseqdown.
This gives the rigidity of control streams with the flexibility of inline control.