Positive lookbehind nonfunctional in `krename` – how to capture single letter in alphanumeric string?

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1 
(?<=\d)T

works at https://regexr.com with 20230409T154230.5543+0100, but doesn’t in krename. Is this expected? I want to convert t into T.

<!DOCTYPE KRename>
<KRename version="1.0"><FindReplaceList rows="1"></Row><Row num="1"><RegularExpression>2</RegularExpression><Find>(?&lt;=\d)T</Find><ReplaceWith>T</ReplaceWith><ProcessTokens>2</ProcessTokens></Row></FindReplaceList></KRename>