SUMMARY
Pressing Windows (Meta) key + . launches and focuses the Emoji Selector ibus-ui-emojier-plasma (called "Emoji picker" in this bugbase). Great! However, if it's already open but obscured by other windows, nothing happens.

STEPS TO REPRODUCE
1. Press [Meta+.]
2. Run another app, e.g. KWrite, and position it over the Emoji Selector.
3. Press [Meta+.] again

OBSERVED RESULT
Nothing happens.

EXPECTED RESULT
The Emoji Selector should become visible and get the input focus, just as it does when you start it for the first time.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 33 KDE Spin.
KDE Plasma Version: 5.20.3
KDE Frameworks Version: 5.75.0
Qt Version: 5.15.1 xcb

ADDITIONAL INFORMATION
If it matters, I have a dual-screen setup with an external monitor plugged into my laptop.
The Emoji Selector does pop on top if I click the desktop background, but it doesn't gain the input focus.
If the keyboard focus is in Firefox or Thunderbird, the Firefox/Thunderbird scrollbar flashes when I press [Meta+.].