[Feature Request] - Improve error message when variable is not found

[knokio]

The error message before sending a request, when some variable is missing is not very clear
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. In any request add some non-existing variable to the body or headers
2. Send request
3. See error: attempted to output null or undefined value

Expected behavior
The error should be clearer: variable not found in body: test_password

Screenshots
These screenshots are one example of this problem.

The request

The environment configuration. Notice how it's missing the test_password

The current error message

Desktop (please complete the following information):

• OS: Mac 10.15.3
• Installation Method: homebrew
• App Version 7.1.1

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[wongstein]

Thanks for the report and the feature request! We are in the process of rethinking our UX and making improvements. This was a great point to make that would improve our Users' experience greatly.

[subnetmarco]

Being worked on in #7227 and will ship in a few weeks.