This tool merges grouped meshes in a level together with the unreal merge capabilities in bulk.
The merging process saves data on the original meshes when merging a mesh so that the merged mesh can be reverted and adjusted before merging again.
Warning: The groups are set by name in the first item in the actor's tags; if anything else is using this tag, they will not be compatible (unless you can adjust where the tags are written in the blueprint)

UI Overview

Step Overview
Groups all selected static mesh actors into one group, so they can be merged into one static mesh.
Adds selected meshes that are not in a group to sleeted meshes that are in a group. (The selection should only exist out of static mesh actor that are not in a group and a static mesh actor that is in the group they need to be added to.)
All selected static mesh actors will be removed from the group they are in.
All groups in the level will be Show/Hidden.