Would like data be transformed before it's return from query api, this help to create data masking or remove sensitive information from APIs return
Hi @zgfeedback! Thanks for sharing your feedback 
I'll share it with our team. Would a query transformer work for the time being? The return value from the transformer you write becomes the value of yourQuery.data in the rest of the app.
Access & customizability is likely dependent on the API, but ideally, you would be having your backend only return data that you are comfortable having available in the user's browser since the return is sent there to be processed with JS (such as transformers) and rendered to the user.
Prefer to Mask certain data before returning it from the API, it reduces data sensitivity and without customising any additional API
Hi @zgfeedback! Just wanted to add that you may find Workflows helpful! You can transform the data in the Workflow and then call your api Workflow via a webhook in your app
Ok noted, but self-host does not have that =(
Hi @zgfeedback Workflows should now be available for all deployments on Retool version 2.117 or later. We have some documentation here
Definitely let me know if you're not seeing it or run into any issues
Not sure if this is helpful for your case, but just noting that our team added an option to sanitize custom headers on the resource set up 
