SUMMARY I have a file with the filename: 00 0000 00.txt (1) For Find and Replace, I can type, the lookahaed function: Find = \s(?=\d(4}) Replace = X So that, when I select "Okay", The Proposed Filename correctly appears: 00X0000 00.txt (2) For Find and Replace, I can type, the lookback function: Find = (?<=\d(4})\s Replace = X However, when I select "Okay", The Proposed Filename incorrectly appears: 00 0000 00.txt When, the correct result would be: 00 0000X00.txt STEPS TO REPRODUCE OBSERVED RESULT The lookback function appears to not work. I have tested the lookahead and lookback functions, several times. The lookahead function always works. The lookback function never works. Please Help. EXPECTED RESULT SOFTWARE/OS VERSIONS Xubuntu 22.04 LTS ADDITIONAL INFORMATION 7am Tuesday 28 2025.