The following widget will help you to do this
You can use the Data Grid widget to select the attendees and set the selection mode to ‘Multi Selection’.
This will let you select multiple attendees at once.
you can do it once you create a meeting and there is multi widget to done that :
- you can use input reference selector widget you can find it al ready at the widget list ,very easy one you will select the data source and right click you can generate the selectable popup page .
-another option the one shared by Stella and also you can use label selector widget and the bellow is the link
I guess bootstrap multiselect more flexible regarding the datasource you have an extra option that you can have the data source through a MF that will be helpful sometimes.
Note: make sure that your using many to many relation between the meeting and people .
hope that will be helpful .