It's already configurable ;-) Unfortunately not well documented right now.
Please take a look to doctrine.ormd2.cfg.xml file. At the end of file you will see:
<!-- #CFU - CamelCase-FirstUpper, #CFL - CamelCase-FirstLower, #UL - UnderLine -->
<template name='association-field'>
<field name="{inverseEntityName#UL}_{inverseFieldName#UL}"/>
</template>
<template name='many2many-field'>
<field name="{inverseEntityName#UL}_{inverseFieldName#UL}" type="integer" required="true"/>
</template>
You can configure association and many to many fields by this template. As comment explains, code after # resolves how name will be generated. So if you want to generate field names like in ORMD1, change #UL to #CFU.
As usual, you can change this settings directly in this file or overload it. One of the best improvements on new ORM Designer2 is that you can override this settings also on per-project basis.
So if you want to use original convention only in one of your project, create file project.ormd2.cfg.xml stored in directory ProjectDirectory/OrmDesigner/custom.ormd2.cfg.xml
(Note: ProjectDirectory is directory where main ORM Designer project file is located).
and insert following content to this file:
<ormd2-configuration xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<orm-configuration name="Doctrine">
<element-templates>
<template name='association-field'>
<field name="{inverseEntityName#CFU}_{inverseFieldName#CFU}"/>
</template>
<template name='many2many-field'>
<field name="{inverseEntityName#CFU}_{inverseFieldName#CFU}" type="integer" required="true"/>
</template>
</element-templates>
</orm-configuration>
</ormd2-configuration>
Regards
L.
Note: If you're using non-standard naming convention "first_Second" name in your entities, ORM Designer convert your name to uppercase/camel case "first_second" or "firstSecond" format. If this isn't required behavior, you can update field template to this format:
<field name="{inverseEntityName}_{inverseFieldName#UL}"/>
(ommit #UL/#CFU from inverseEntityName. After that ORM Designer only copy entity name without any name conversion)