Resolution:
The following features are not in the current mapper but we are looking at including them in a future release

- Foreach() and selecttree() support in the mapper
These functions were supported in MB 2.5 but are not currently supported within the 3.2 mapper.
- Sum or accumulator functionality is not available
With the current version you cannot map a field in the output as the sum of fields in the input, whereby the sum is built from a repeating input, not just different fields
However,  there is a workaround whereby you can use the sum() function in a function plugin outside the mapper.  This value can then be passed to the mapper as a non-schema input and mapped to the output.
- Filtering
While you can set different filtering policies when (structurally) mapping input node A to more than one output nodes, the output nodes must be peers.  If these output nodes have a child - parent relationship, users are restricted to using the same filter
- Mapping a repeating node to a non-repeating node
The first occurrence of the repeating node is mapped.  In the current version, this is not configurable though you could use a filter to achieve this result if the input is somehow unique.
- Nested Mapper  (i.e. a mapper within a mapper)