A… I read wrong. I thought you wanted to show a digital time. Unfortunately I do not use version 1.4.20. I think you cannot affect the format a complication, the data will come directly from the watch/app. Please show screenshots from WFS.
I’ve created a test case now. Would be useful to get Ron’s (@r.liechty_SDP) input and I’ll create a bug report if it’s not just user ineptitude!
The test case just has a ‘Line’ complication set as ‘Fixed’ with the default provider being world clock. It displays fine in the WFS preview window but in the hour after midnight in the selected timezone the watch it displays 24:xx as the time. I attach a screenshot saved from my GW4 when I had the time zone set to Hawaii, which happened to be just after midnight there…
One other thing. In WFS 1.4.20, WFS sets the “Text” field of the complication to be the time, and the “Title” field to be the Time zone label, but on the actual watch device these values are reversed. See WFS preview window capture of the same watchface below.