In "Find & Replace" no Unicode escape sequence (\u####) is recognized for the text to substitute. This makes is impossible to solve some replacement tasks, like replacing a paragraph break with a line break.
Steps to Reproduce:
1. Have a text with '°' in it
2. Try to replace '°' with a line-break (not a paragraph break)
It does not work (it's not possible)
It should work (it should be possible)
User Profile Reset: No
See also https://ask.libreoffice.org/en/question/55740/i-am-trying-to-replace-the-paragraph-charachters-with-line-break-cant-figure-it-out-dosent-have-option-for-paragraph-break-or-does-it-or-i-cant-figure/
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0
The hex Unicode value \u00b0 search string picks up the "°" in a Find & Replace dialog with Other Options -> Regular Expressions checked. While our "\n" replacement results in paragraph breaks.
This works as expected.
On Windows 10 Home 64-bit en-US (ver 1709)
Version: 188.8.131.52 (x64)
Build ID: 32c8895c6cae21571f364dbb059f419a743ee44d
CPU threads: 4; OS: Windows 6.19; UI render: GL;
Locale: en-US (en_US); Calc: group
Rereading this, guess this could be considered a duplicate of bug 106137 if you are asking to parse the Unicode for use in the replacement string.
The Replace string can not be RegEx based because our Regular Expression support in the Find & Replace dialog uses ICU libraries for its direct Unicode support.
The Replace field does not implement its own RegEx beyond using the ICU pattern matching buffers available from Find .
In the see also, devs suggest they may be able to provide new parser to enter replacement text with \u or \U syntax but that it would not be fully functional RegEx.
*** This bug has been marked as a duplicate of bug 106137 ***