1) in Writer write Hello, press Ctrl+H for Find&Replace dialog
2) check Regular expressions, Find: e, Replace: \\n
3) do Replace All
It will replace the letter "e" by Enter (like for \n in the Replace), but correct replacement for \\n is string \n.
For tabulator \t it replaces correctly. \t will do correctly tabulator, and \\t will do correctly string \t.
Version: 220.127.116.11.beta1 (x64)
Build ID: 828a45a14a0b954e0e539f5a9a10ca31c81d8f53
CPU threads: 8; OS: Windows 10.0 Build 17763; UI render: Skia/Raster; VCL: win
Locale: cs-CZ (cs_CZ); UI: cs-CZ
I confirm it with
Version: 18.104.22.168.alpha0+ (x64)
Build ID: 315c7570c4a72f4c834086082825533b1e50d1bf
CPU threads: 4; OS: Windows 10.0 Build 19042; UI render: Skia/Raster; VCL: win
Locale: de-DE (de_DE); UI: en-GB
Also in Version 22.214.171.124 (Build ID: e183d5b)
I think is inherited from OOo.