SUMMARY
[Add a new Panel][Duplicate a panel] Duplicate a layout of a currently chosen panel/Mirrored panels.
A user may want to have a panel with a duplicated layout screen, and have it's changes carried over.
User may want to right click on his panel of choice, trigger a context menu of the panel, and choose to duplicate a panel and it is layout.
Rather than selecting from a list of prefabricated choices.

[Add a new Panel][Mirror a panel] User may also want to "mirror" panels.
Mirrored panels would have their changes carried over to a mirrored panel and vice versa, with exclusion of settings like panel position, and length.
This is akin to how windows desktop panels work by default.

I noticed this while hooking up another monitor, and I can agree it is not really something done all that often, but.

[Desktop settings auto-manager]
[Panel settings auto-manager] Which brings me to another topic, while some multi-monitor setups are advanced, while hooking up a new monitor some would want to have a panel creep up on a specific side for said new monitor.
I propose it should be a setting, whereby the panels auto adjust themself to a certain place, this goes hand in hand with panel mirroring and duplication.
There should be variety of settings which accommodate different user set ups.

Examples of how users might want to set it up:
User wants a new default panel to show up on the bottom of the screen of each new monitor.
Monitors placed on top of each other, where the panels spawn on the bottom most(at the bottom) and top most(at the top) monitor.
User sets up that an auto hiding, panel that's like a dock in the middle of the screen, user then sets up this panel as showing up on every new 
User sets up so that monitor layout sets up a panel on the left and right edge of the edge monitors: Say in a 3 monitor set up one after another, this sets a panel on the left side of a left most monitor and right side of the right most monitor, the panels swap monitors when their position in display settings is changed.

[Image Wallpaper auto-manager]
By default when hooking up another monitor(assuming it won't get selected as a new primary), plasmashell sets up a pure dark black wallpaper, I personally think the default should follow some logical set of rules[if a wallpaper is long enough by default try to extend it onto a new monitor, duplicating a wallpaper is also an option for most setups, setup one of the default wallpapers when the primary monitor wallpaper isn't long enough for a newly hooked up monitor].

OBSERVED RESULT
While my panel isn't deriving hard from the default options to pause a trouble for me, I can't speak for others.
I would really want an ability to mirror my panel including icon size, and widgets that have been placed on it.

EXPECTED RESULT
I can easily manually duplicate/mirror panels.
Or when I hook up a new monitor plasma sets up the panel for me.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.10.16
KDE Plasma Version: 5.20.5
KDE Frameworks Version: 5.79.0
Qt Version: 5.15.2