At the moment it is not possible to move a widget down into the space left or right of a centered Taskbar? It just refuses to get moved down, or do I miss something.
I would like to do so, else centering the taskbar creates currently, in my opinion, mainly unusable space left and right of it.
I have a comparable problem. There is an exclusion zone corresponding to the panel. Personnaly I have a panel reduce to the side, autohiding, I want to be able to put widget on that zone and the panel also prevent me to put widget on other side on the border of the screen.
I wonder why it is designed like that, is it a technical problem? or a choice ? because I can’t see the interest in that.
Nice new edit mode that shows the full screen without any obstacles, now with invisible obstacles. 
tbf, the old one was like that too.
any panel, regardless of size, will occupy that entire screen edge as a stayout zone as thick as the panel… i think that’s just how plasma calculates the size of the remaining desktop for widgets.
i cannot put the clock in the lower corner even tho the bottom panel is resized to show the desktop in that area.
icons can go there, but not desktop widgets.
Never tried a centred Taskbar/Panel with Plasma 5, just now with the new edit mode that looks even more separated from the rest.
No they can’t.
Well technically they can -
but only until logout, after reboot/relogin all icons go magically to the top of my primary display. Auto-Sorting disabled of cause and even when locked (should be a, if I remember correctly, long known bug that maybe transitioned into a design choice or rather “you shall not have desktop icons anyway, lowest of low fix priority”)
And the “workaround” to place Icons fixed on specific locations, you may have guessed it already :trumroll;, a widget. 
they can go there… didn’t promise they would stay there 
yes, if you want total control over where things go (and stay), then widgets… except they can’t go there 
By the way the problem is not only with centered panel but all panel not maximized. My impression is that panel and widget are on the same layer and to be able to freely place widget they should be somewhat on 2 independant layer. Maybe it is what permit that widget can be move between desktop and panel.
Also I had this problem on plasma 5 and I expected some change with plasma 6 but not. I suspect it to need a little bit of work and that would introduce some change and compromised other fonctionality. But maybe it is worth a post on bugs.kde.org.
