Could you add World Clock, that looks like W7 clock (or, at least, like Gnome clock)? Attached a screenshot of clock I want to see in KDE. Sad, that KDE still doesn't have an World Clock applet. Reproducible: Always
Created attachment 99031 [details] W7 World clock W7 World clock
So what we basically want is the ability to add multiple time zones to Analog Clock? Or you mean as an option to display multiple in e.g. digital clock's calendar popup?
The latter.
I don't think this will be worked on anytime soon *but* you can add multiple timezones to digital clock which will then show up in its tooltip. You won't get a nice analog clock for them but it should be close enough.
This is possible now. If you define multiple timezones in the applet, it will display a clock per timezone in the pop-up. They'll be digital clocks, not analog, but they're there now. This feature was added in Plasma 5.19 IIRC, and the layout was improved in 5.20.