You do not need workspaces for that. The Alt+tab task switcher can be set to work across desktops, so you can simply switch to a window on another workspace using Alt/Super+Tab
Option 1: Minor change
You could achieve this simply by changing the Alt+Tab Window switcher, that stock Ubuntu uses by default, to cover all workspaces:
gsettings set org.gnome.shell.window-switcher current-workspace-only true
Reset this setting to the default setting by changing set
to reset
and leave out the value of the setting (true
in this case).
This quickly may become impractical because the list of windows quickly can become large. Unless you are very disciplined and close any window you not immediately need, you may prefer to try the way it is handled in stock Gnome.
Option 2: Major change: revert to behavior of Stock Gnome
In stock gnome, you switch between applications across desktops with Alt/Super+Tab, and between windows of the same application across desktops with Alt/Super+`. This is how you change task switching in Ubuntu to behave like stock Gnome Shell:
gsettings set org.gnome.shell.app-switcher current-workspace-only false
gsettings set org.gnome.desktop.wm.keybindings switch-applications "['<Super>Tab', '<Alt>Tab']"
gsettings set org.gnome.desktop.wm.keybindings switch-applications-backward "['<Shift><Super>Tab', '<Shift><Alt>Tab']"
gsettings set org.gnome.desktop.wm.keybindings switch-group "['<Super>Above_Tab', '<Alt>Above_Tab']"
gsettings set org.gnome.desktop.wm.keybindings switch-group-backward "['<Shift><Super>Above_Tab', '<Shift><Alt>Above_Tab']"
gsettings set org.gnome.desktop.wm.keybindings switch-windows "[]"
gsettings set org.gnome.desktop.wm.keybindings switch-windows-backward "[]"
Again, you can undo as indicated above.
Option 3 - what you actually asked: change key binding
Change the relevant shortcut keys in "Settings - Keyboard".