[Feature Request] Support multi-selection of extension sources across different VS Code Profiles

[rfhits]

Currently, in VS Code's Profile configuration (within the "Contents" section for Extensions), the "Source" option only allows selecting a single Profile (e.g., "Default" or a custom profile like "java") as the extension source for the current profile. This means users are restricted to using the extension set from one specific profile at a time — there’s no way to combine extension collections from multiple existing profiles.
This limitation creates inefficiencies for workflows that need mixed extension sets: For example, if I have a "Default" profile with general-purpose extensions and a "java" profile with Java-specific tools, I can’t create a new profile that uses extensions from both. I either have to duplicate extensions across profiles (wasting effort and storage) or manually maintain overlapping extensions (which leads to inconsistencies).
I’d like to request adding multi-selection support for extension sources in Profile settings. Instead of a single dropdown for the Extensions "Source", let users select multiple Profiles; the current profile would then include all extensions from the selected source profiles.
This change would make VS Code Profiles far more flexible, cut down on redundant extension setup, and let users mix-and-match extension sets to fit their specific project/workflow needs.