1)If you have tabs in caption and the now playing list is docked in right sidebar the header is removed to make it flush with main panel. So with the header gone Steven had to put the duration somewhere else and he chose the status bar. I guess that for consistency he made it show in the status bar even for layouts where header is visible.
Since the most important thing about this header is moved to the status bar, why not just removing this "useless" header when docked to the right (whatever the position of the tabs: main panel or titlebar) and extend the new tabs/toolbar to the right when you tick "Horizontal (Left + Main Panel)"?
- more space for tabs and/or icons! Since two bars are merged, this extra space would be welcome.
- more consistent:
-> Right panel have an header, left one haven't
-> icons and search box are staying at the same position, whatever the status of the right panel (expanded or not)
Here 2 screenshots I made (1 year ago) in
this topic:
vs.
2)i have added an extra option in the toolbar configuration dialog so that the toolbar buttons can be displayed on a separate row when tabs are docked in the main panel ie. effectively the old layout
Thank you!
3) Could we have a skin element (or the ability to choose our own icon in icons folder) for this new "group icons into one" button, please?
4) About this new horizontal icons popup (when you press the "group icons into one" button), why not something like google?

It's not really a wish, I'm OK with the actual icons popup. Just giving an idea about an alternative layout (I forgot to hide the text under each icons...). IMO, it looks better, it's more intuitive (vertical orientation, like a dropdown menu) and it's easier/faster to click.
5) One last thing about this icons popup: I think that the close button is useless since:
- clicking a second time on the "group icons into one" button close the popup (good enough and faster)
- performing another action auto-close the popup (even faster)
So, you'll never use this "close" button!