kshepic Thanks for posting your question in Microsoft Q&A. The workspaces aren't surfaced to the developer portal and the reason has been described here. However, you can publish API/Products from the workspaces to the develpor portal.
Based on the description, you would like to know how to develop a portal custom widget in the repo separately Dev vs Prod for the managed version. Currently, you can create a custom widget in your own repo/environment based on scaffolder and tools and configure the widget in the developer portal. To make the widget available in the production, you would need to republish the developer portal but unfortunately, there is no option to have two different repos for the managed version (doc reference).
In general, it is recommended to have different APIM instances for each environment such as Dev, Staging and Prod and you can maintain the developer portal changes for each environment accordingly. Then you can use automated migration script to move the changes between two APIM instances and refer Automate developer portal deployments for more info.
For any feedback regarding this feature, please submit it via https://aka.ms/apimwish to the product team and others with similar interest can upvote your idea. This will help our product team understand the customer interests and prioritize the features accordingly. I will also submit your feedback to our product team internally. I hope this helps and let me know if any questions.
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