TYPO3 Core

I tried several translation key combinations to translate the previousButtonLabel and nextButtonLabel only for a specific form definition, but it seems this is currently not possible.

What does work (sets label for every form):

<trans-unit id="element.SummaryPage.renderingOptions.previousButtonLabel">
    <source>back</source>
</trans-unit>

What doesn't work:

<trans-unit id="<form-identifier>.element.SummaryPage.renderingOptions.previousButtonLabel">
    <source>back</source>
</trans-unit>
<trans-unit id="element.<form-identifier>.SummaryPage.renderingOptions.previousButtonLabel">
    <source>back</source>
</trans-unit>
<trans-unit id="element.SummaryPage.<form-identifier>.renderingOptions.previousButtonLabel">
    <source>back</source>
</trans-unit>
<trans-unit id="element.<form-identifier>.renderingOptions.previousButtonLabel">
    <source>back</source>
</trans-unit>

I would have expected to translate these the same as the submitButtonLabel:

<trans-unit id="element.<form-identifier>.renderingOptions.submitButtonLabel">
    <source>Send message</source>
</trans-unit>

(the order of this translation key seems odd anyway, as the form identifier is the second part here, contrary to prepending it to keys for field labels like <form-identifier>.element.<element-name>.properties.label)

Is this a missing feature or do I use a wrong translation key?