How to store setting for SharePoint Extension (sppkg)?

Question

I need to store site setting for new type of SharePoint extensions (spfx, .sppkg file). Are there any special approach to do this? Here is what I need to store:

1. Store settings that user can not see and edit. For example some
   configuration options for internal usage and a license ID or license file.
2. Store settings that user can edit (typically SharePoint site administrator or a person that installed the Extension).

Answer 1

1) To store such settings, would suggest that you make use of SharePoint Tenant properties. They allow you store key/value data and since they are tenant properties, they are available to be used across the site collections.

These can set by SharePoint admins only using PS command as:

Set-SPOStorageEntity -Key "LicenseId" -Value "0000-0000-0000-0000" 
-Description "License for a specific purpose"

2) To store a setting that a user can edit, would suggest that you keep it simple and create a custom list with necessary columns and break the inheritance of that list to ensure that only a particular set of user's can modify its data.