Hi @GaneshAn2
I would refrain from using more than one Launch library at the same time to rule out any side effects since they will both be declaring a window._satellite object, and likely one overwrites the other.
What keeps you from sending the WebSDK calls in you old launch library?
if this is just a small POC, maybe duplicate your old launch property, do the SSF modifications in there and inject the copy into your website.
Cheers from Switzerland!