Kitbashing
Open Stand-In Outliner Window / Stand-In Outliner.
Select Static meshes you want to make a kit from.
Select Create in the Stand-In Outliner.
Pick Near Pipeline.
Build Stand-In
Save to package.
Select path.
Repeat for another kit
Bash kits together to form new kits.
Add casters. Optional Material Merge
Adjust Output Texture Resolution. Optional Material Merge