Understanding Society User Support

Hi there,
Thank you for previously helping me with merging USOC waves.
Unfortunately, my work PC does not allow me to store files as large as the file created when all 8 waves of USOC are merged.
In light of this, is it possible to select 2 or 3 variables only that I want to take from each wave and merge into one data file?
If so can you help with how to do this please?

Many thanks, appreciative of your useful, efficient responses on this platform!
Erica Holt-White