Replacing indents by “true” tabs is a sin against good use of document processors. Whether indents are hanging or “normal”, or even if there is no indent, setting the desired indent spacing is just a matter of customising the paragraph style.
When you open a paragraph style definition, tab Indents & spacing
allows you to set the horizontal limits of the paragraphs within the paper sheet margins. Left limit is called Before text, right limit After text. The “mysterious” First line is where you set indent: a positive value results in the usual indent and a negative value results in a hanging indent.
All you have to do is set First line to the desired value.
Of course, if your friend use LO as a mechanical dumb typewriter, i.e. typing all text in the default paragraph style Default Style, not making any difference in various paragraphs, achieving vertical spacing with empty paragraphs, the situation is hopeless. Text should be typed as Body Text. Otherwise adjusting Default Style will modify all other paragraphs, including headings, because they all inherit its properties.
To clean the mess, your friend will have to properly style his/her document. After that, playing with style definitions formats the document in a snap.
Read the freely downloadable guide or, at least, use the built-in help.
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EDIT 2019-07-01
Search-and-replace operates on individual paragraphs (more precisely on text between excluded paragraph marks). Consequently, you can’t search for paragraph marks. Eventually you can search for line feeds which are “ordinary” control characters which don’t break paragraphs.
Since you need to detect start of paragraph (which is a “virtual” character), you need to enable Regular expressions in Edit
>Search & Replace
. Search for ^(.)
, i.e. any character at beginning of paragraph. Replace with \t$1
, i.e. a HT (tab) character followed by what was captured between the parentheses.
Press Replace
or Replace All
.
Note that empty paragraphs are not affected.