ah, thx for the other reply :)
I'm not sure how it would be setup once imported in Unreal, but you can add a second UV channel for lightmapping in Blender through the data tab as shown in this video: https://streamable.com/ut6u7
You'll probably want to play around with the smart project settings to add more padding between UV islands or even manually unwrap the lightmap, but this is the basic idea.