You can change this behaviour either in dconf editor:
org -> gnome -> mutter and uncheck the box " workspaces-only-on-primary"
or if you do not have installed dconf-editor you can use following terminal commands:
gsettings get org.gnome.mutter workspaces-only-on-primary to check the current setting. Probably it is "true".
gsettings set org.gnome....
This is intentional for the reasons you pointed out. At the moment we can't have independent workspace switching. The window manager sees multiple displays as one big workspace in Luna. This can be frustrating because one of the big benefits of having another display is to have a place for things you always want to see like documentation or chat or your ...
You can disable dynamic workspaces:
gsettings set org.pantheon.desktop.gala.behavior dynamic-workspaces false
You can set the number of workspaces wanted to NUMBER:
gsettings set org.gnome.desktop.wm.preferences num-workspaces NUMBER
(Nevertheless, even if you use dynamic workspaces, there are actually no "empty workspaces"…).
You can achieve this by assigning a keyboard shortcut to "Toggle on all Workspaces" in System Settings -> Keyboard. Now when pressing that keyboard combination with your Pantheon Terminal active, the terminal window should appear on all workspaces. Press that same combination again, and the option should get disabled.
I'm not sure what solution you are actually looking for. If you wanted to restrict the icons to show only from current workspace, you can achieve that with plank very easily.
First bring the plank preference with the follow command. (If you have the preference icon in plank docked, that's fine)
Head over to the Behaviour tab and ...
With dynamic workspaces enabled (which is default in elementary OS), you cannot create workspaces explicitely but
a new empty workspace is created by switching to the right of the rightmost existing workspace or
a new workspace is created by moving a window right to the rightmost existing workspace.
If you disable dynamic workspaces (via the command line ...
Nope, without custom scripting, the OS only supports switching between windows in a workspace ("Switch Windows" in Settings > Keyboard) and switching between workspaces (org.pantheon.desktop.gala.keybindings cycle-workspaces-next), but not apps across all workspaces.
What you can do, however, is set "Show All Windows" in Settings > Keyboard > ...
Here is a list of many keyboard shortcuts, starting with the ones for managing windows and workspaces.
Alt + f4
Alt + f5
Windows Key + Up Arrow
Windows Key + H
Windows Key + Ctrl + Left Arrow
Windows Key + Ctrl + Right Arrow
Alt + Tab
It is possible to create a keyboard shortcut for this setting which seems to work for any window, including those without title bar menu. It's in System settings > Keyboard > Shortcuts > Windows > Toggle on all Workspaces and it isn't assigned by default.
I don't believe there is a way to remove workspaces other than to move or close the app that is sitting in it. To prevent new ones from being created you just need to avoid "activating" one with the keystroke.
You cannot use this gnome extension because you are using elementary OS (pantheon, gala) and not gnome-shell.
I am pretty sure that you cannot do this under elementary OS, because this functionality is not implemented (and it uses only a single row of workspaces).