I observed myself during my daily work and realised that I keep switching between Excel and SQL Developer. Why?
Because Excel has a feature 'Remove Duplicates'!
So I paste the values into Excel, remove the duplicate values, add apostophes and commas via a formula so that I get a list like
'FR123456789',
'DE123456789',
'US123456789'
which I then copy an paste back into SQL Developer to continue my work.
It would be great if SQL Developer could do this tedious task for me - maybe with our without apostrophes depending on the data type.