Line length in multi-line strings

I need to limit the number of characters a translator can enter per line in the following:

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<text kind='TEXT' id='01364' linelen='30' line='002'>
<val>
Keilrippenriemenscheibe mit<br/>
Freilauf und Schutzkappe
</val>
</text>
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

 The attribute linelen gives the maximum number of characters per line. Each line ends with <br/> and a line break.

Can anyone suggest a way to do this in Studio?