I have made some changes to the way MergeUi works and also moved it into a new repository (https://github.com/GoEddie/SSDT-DevPack).
The way MergeUi used to work was that it enumerated the schemas and tables in a project and let you create a merge statement in the post-deploy script. The problem with that is that you may want to have different versions of the table for different environments or you may want to put the merge in a different script and either reference it using :r imports or not reference it at all.