Studio will duplicate form content each time when press ctrl+s(cmd+s on mac) in extend screen visual designer.
Step1, create an empty screen, then use following xml. You have to modify DC class and property names.
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<window xmlns="http://schemas.haulmont.com/cuba/screen/window.xsd"
focusComponent="form">
<data>
<instance id="baseclassDc"
class="com.company.uimodel.entity.Baseclass"
view="_local">
<loader/>
</instance>
</data>
<dialogMode height="600"
width="800"/>
<layout expand="" spacing="true">
<tabSheet id="tabSheet">
<tab caption="Tab" margin="true,false,false,false" spacing="true">
<form id="form" dataContainer="baseclassDc">
<column width="30%">
<textField id="nameField" property="name"/>
<textField id="nameField1" property="name"/>
</column>
<column width="30%">
<textField id="ageField" property="age"/>
<textField id="ageField1" property="age"/>
</column>
<column width="40%">
<dateField id="birthdayField" property="birthday"/>
<dateField id="birthdayField1" property="birthday"/>
</column>
</form>
<hbox id="editActions" spacing="true">
<button action="windowCommitAndClose"/>
<button action="windowClose"/>
</hbox>
</tab>
</tabSheet>
</layout>
</window>
Step2, extend this screen.
Step3. open extended screen in Visual designer. Press ctrl+s(cmd+s on Mac) to save extended screen.
You will notice the ext-screen have multiple columns duplicate generated.
Using Studio 11.1 Bundle version.