According to: https://help.libreoffice.org/7.2/en-US/text/shared/01/06040100.html
Delete blanks and tabs at end and start of lines
Removes spaces and tabs at the beginning of each line. To use this option,
the Apply Styles option must also be selected.
0. Tools > AutoCorrect > AutoCorrect Options - Options tab
uncheck all [T] and [M] options, except for following two
"Delete spaces and tabs at end and start of line"
1. Make sure: Tools > AutoCorrect > While Typing (is enabled)
2. Use "Default Paragraph Style" or "Text Body" PS for all tests.
3. Enter some text with spaces and/or tabs at beginning and end, press Enter
Expected result: any spaces and tabs at beginning of line (according to "help") and at end ("according to option label") should be removed, and no change to PS.
Actual result: converted to "Text Body Indent" but no tabs or spaces are removed (at beginning or end).
1. Also tested with [M] ("Apply Styles" is not needed in this case).
2. Afaict, this option is functionally equivalent to "Delete spaces and tabs at beginning and end of paragraph"
3. Both options have been present since at least OOo 1.1.0,
Critical question: What is "intention" or "utility" or "value added" of this AC option in the bigger picture of other options? (I could not imagine anything).
Forgive my cynicism, but looks like:
"Delete spaces and tabs at end and start of line" was a precursor to
"Delete spaces and tabs at beginning and end of paragraph" (and did not work),
and then someone forgot to remove the precursor, after the "paragraph" version was implemented.
Maybe this "option" should be removed? or its true intention/value rediscovered and re-enabled.
NB. The "actual" result can also be obtained without the option being set.
Because, at present, Default is converted to Text Body automatically (with no options set) (see bug 90507), then lines with spaces or tabs will be converted to Text Body Indent anyway.
iow -- not clear that "Delete spaces and tabs at end and start of paragraph" option has any currently actual function.