Problem/Motivation
We want recipe authors to have a flexible way to set where in the target region the block should be placed, instead of using a weight value that may not achieve the intended effect. For example, a recipe author may intend for a block to be place first or last in the target region.
Proposed resolution
Allow an author to specify the placement within the region. If following the approach used for the config actions elsewhere, this should use a key other than "weight", but the config action code will determine the numerical weight value needed to achieve the intended placement within the region. There may also be value in allowing the placement to reflect an ordinal position within the series (such as second, third, etc) but if that proves complicated it could be deferred to its own, separate issue.