In this example, I will condense a list of paired-down postcodes into a short list by removing all the duplicate entries.
First, paste your list into LibreOffice
Then, go to Data > More Filters > Standard Filter
TIP: you may need to select the column or data range before applying the filter.
Set up the filter as follows:
Field name: none
Value: Not Empty
Click the options expander and choose
No duplicates and copy results to (choose a convenient empty cell).
Click okay. You should now see a the list condensed, with all duplicates removed.