Does the CDB API, or the Pro version of it, support the concept of Layouts as used in the CAE Update Manager/CDB Server product?
Based on a preliminary review of the code it looks I would have to write code to handle layouts myself and merge data from multiple databases to find the best/most current version of the data.
This is a CAE product questions. CDB API support the CDB specification. There is no concept of "layouts" in CDB - not under this name.
However, the CDB API does support the CDB concept of "Versions" (also called chaining - see CDB spec 3.2 - volume 1 - section 3.2). THe "Configuration management" is activated via the file Metadata/Version.xml and Metadata/Configuration.xml (CDB 3.2). Using those files, as per the CDB specification, to "chain" multiple CDBs, the CDB API will lookup any request into the provided chain automatically.
As such, if what the tool you reference (Update manager) implements "layouts" by creating the CDB compliant chain, the CDB API will "find the most current version of the data" as you say.