Is It possible to make workspaces in Unity act like they do in GNOME Shell?

Problem:

Unfortunately not yet. There has been some talk about dynamic workspaces in Unity, but I don't know of any concrete plans for this as yet.

Partial solution:

While dynamic workspaces is not yet a feature of Unity, you can get a similar feature pretty easily. This solution uses a script that was posted on Webupd8, so I cannot take the credit for the actual script and .desktop file, but the Keyboard Shortcut method is mine.

First create a script (text) file with this content:

#!/bin/bash

case $1 in 
rows)t=v;;
cols)t=h;;
esac;

check=`gconftool-2 --get /apps/compiz-1/general/screen0/options/${t}size`

if [[ ! ($2 = - && $check < 2 ) ]]
then
    [[ $2 = [-+] ]] && gconftool-2 --set /apps/compiz-1/general/screen0/options/${t}size --type int $(( $check $2 1 ))
fi

• Save it as workspaces (no file extension).
• Right click on the file and click properties.
• Mark it as executable in the file properties.
• Now move it to /opt:
  Either:
  • Run sudo mv workspaces /opt in a terminal,
  • or press alt+f2. Type gksu nautilus /opt. When the new window opens, cut and paste the script into that folder.

Keyboard Shortcuts Method:

Now, you can assign some shortcuts to enable adding and removing workspaces.

• Open System Settings.
  
• Click on "Keyboard".
  
• Go to "Shortcuts".
• Click "Custom Shortcuts", and click on the plus button (highlighted).
  

• You can choose your own shortcuts that suite you, but here is what they need to contain (One command per shortcut):

  1. /opt/workspaces-shortcuts rows + | (Adds a row)
  2. /opt/workspaces-shortcuts cols + | (Adds a column)
  3. /opt/workspaces-shortcuts rows - | (Removes a row)
  4. /opt/workspaces-shortcuts cols - | (Removes a column)

Quicklist Method:

You can create a .desktop file that does all of these functions for you in two clicks.

Create a new text file and enter the following:

[Desktop Entry]
Version=1.0
Name=Workspaces
Comment=Change Workspace Numbers
GenericName=Workspace Editor
Terminal=false
Type=Application
Icon=desktop
X-Ayatana-Desktop-Shortcuts=AddRow;RmRow;AddColumn;RmColumn;

[AddRow Shortcut Group]
Name=Add Row
Exec=/opt/workspaces-shortcuts rows +
TargetEnvironment=Unity

[AddColumn Shortcut Group]
Name=Add Column
Exec=/opt/workspaces-shortcuts cols +
TargetEnvironment=Unity

[RmRow Shortcut Group]
Name=Remove Row
Exec=/opt/workspaces-shortcuts rows -
TargetEnvironment=Unity

[RmColumn Shortcut Group]
Name=Remove Column
Exec=/opt/workspaces-shortcuts cols -
TargetEnvironment=Unity

• Save this file as workspaces.desktop and mark it as executable.
• Move the file to ~/.local/share/applications.
  • You can do this by opening the file manager, pressing CTRL+L (the letter) and typing the address (it will autocomplete), then pressing enter.
• Drag and drop the file to your Unity launcher.
• When you right click on it, it will give you the option to add or remove rows and columns of workspaces.
  

How to make it more like GNOME Shell:

• Open Compiz Config Settings Manager (install if you don't have it already)

  sudo apt-get install compizconfig-settings-manager
  

• Go to General Options and click Desktop Size.

• Set the "Horizontal Size" to 1.
• Set the "Vertical Size" to 2.
• When you need more workspaces you can use your Keyboard Shortcut or the Quicklist.