When making changes to the WBS, that means adding, deleting or editing existing weight groups, you have two alternative ways of doing it:
1.
Use the designated GUI for editing the WBS, see this help article: https://shipweight.com/wp-content/uploads/software/SWwebhelp/index.html?documents_defineweightgroups.html
Restart ShipWeight for the WBS to be updated.
2.
Alternatively you can do it by going via the system database tables. See this help article: https://shipweight.com/wp-content/uploads/software/SWwebhelp/index.html?documents_customizingtheshipweightsystemdatabase.html