From the secret page, click "Add Secret to Workload". The radio button for environment has a typo.
*** Bug 1803842 has been marked as a duplicate of this bug. ***
Now is “Environment Variables” 4.4.0-0.nightly-2020-02-17-211020
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2020:0581