Featureworks is a fantastic feature included in SW Premium (and maybe others?).  It takes an imported solid model, such as STEP or IGES & figures out how you might draw the part in SW - then converts it from a dumb 'Imported part' to a native SW part which you can easily edit / re-use.

Unfortunately, it only works at part level, not assemblies.  Many imported parts come in as Assemblies, often with hundreds of parts.  Your only alternative is to go through the assembly & run FeatureWorks on all of them.

I thought I'd like it automated - so, here it is!

It's based on the fantastic code  by Md Rakibul Islam:

https://forum.solidworks.com/thread/228404?commentID=929366#comment-964875 

Which Deepak pointed me in the direction of, having failed to make this work through regular API calls (Cheers Deepak!).

It will not convert Surface Models - only Solids.
It seems to work well on STEP & IGES files from most vendors as well as IFC Structural Steelwork.  Sadly it doesn't make them into Weldments, just extrudes.

It will potentially let you open & use an assembly from a future version of SW, if it's saved as STEP.  I've used it to convert a 2021 file to a workable version a friend can use in 2017.  He will have to re-add the mates but that's better than re-drawing the whole thing!

FeatureWorks doesn't always get it perfectly correct (so check the parts it creates) but it does a pretty good job.  Occasionally it pops a dialog telling you it cannot convert a part - just click OK.  You'll have to figure out that one yourself.

It's also pretty s-l-o-w - Go & make Coffee while it thinks about it!

Si