When you go into the find/replace dialog, click on 'More Options' and
tick the 'Regular expressions' box. A list of common regular
expressions can be found at
help.libreoffice.org/.../List_of_Regular_Expressions

For instance, to find a tab - or replace with a tab - use \t in the
relevant box.

Update.

A little more digging has unearthed the nugget that, with regex enabled,
paragraph breaks are found/replaced with a '$' symbol. Should you actually want
to find/replace a dollar symbol, you need to use '\$' or switch regex off.

That is a strange request. How does a search find a key stroke. Never
come across that

It is strange though. Using \n and doing a Search for a
shift+enter it finds the shift+enter. Placing a \n in the Replace field and
a paragraph, enter or return, is used to replace the shift+enter. Same
thing, \n, in the Search and Replace fields.

When doing a Search for a paragraph, enter or return using \n and it finds
nothing. I guess this is so you don't replace ANY paragraph markers with
something else using Search/Replace.

Anyway, this is a great help. In the past I was able to replace the TABs and
shift+enters with a paragraph mark in, excuse me, WORD.

Ian, while an Enter is just a key stroke, so is A, B, C, etc. on my keyboard
but all are represented by ASCII, will now unicode, anyway...

I am well aware of the code representations.

I don't know how you find all the little goodies but I sure do
appreciate them.

This brings up another question. I have use Google but have not been able to
find out how to enable or disable regex. How do you do that? Where is it at?

I was rather tired and being a bit lazy when I made that
post. Regex is a short for regular expression, so in the Find dialog,
go to More Options and tick the Regular Expressions box - it should be
'sticky' so you won't have to change it every time you find/replace.

I thought Regex was short for register extension or register ex(something).
Looked through all the Tools>Options settings, looked in Help and on Google
obviously with no answers.

That works great, actually quite simple. I always thought there should be a
simple way to do that kind of find/replace.