The below steps will reduce a SPPKG to only select Features and WebParts we want to keep. Every SPPKG file is actually a ZIP with XML manifest and subfolder for each WebPart and Feature. Extracting the SPPKG as ZIP allows us to review the internal content, enumerate all Features, and then select ones to keep in a final compressed ZIP file (SPPKG file).
If you want to upload only a few WebParts from a SPPKG package to Office 365’s App Catalog then check out the video below.
Cheers!
