To initiate several voice calls to several groups at the same time from Dispatcher Console, you need to use possibilities of Custom Consoles which can be also created on Dispatcher Console. Go to Settings->Custom Consoles->Add.
Please see the screenshot below:
You will use the following elements:
PANEL - Panel defines in which groups call will be initiated. The Panel element is used for uniting several elements.
Radioserver needs to be used to add groups to the created Panel (in my example, I use IP Site Connect with 2 wide area channel slots and I need to make a call to All subscribers from Both slots, so I added All Call from both slots).
PTT - The PTT element is used for a multiple-user call. If it is located inside the panel, then clicking the PTT element makes a call to all the subscribers located within this panel.
To open created console, go to View-> and choose the name of the Console.
To initiate call to all groups inside the panel, click on PTT Button or hold Space tab (depending on the settings).
Here is also a screenshot of Custom Console in operating mode: