Maybe there is a vocabulary problem here.
Endnotes in Writer are similar to footnotes except they are gathered at the end of the document or section. Notes, generically, are side remarks or comments which are written away from the main discourse so that it does not obscure it or distract the reader with not directly relevant points.
Citations are another matter. They point to sources giving information about author, book title, publisher, date of issuance, … Generally, this is associated with a database for ease of insertion into text. You can also filter the database to limit the amount of information in the edited references.
You manage this in Writer with the Bibliography feature. You control what gets into it through the “bibliography database”. You can’t really choose the format of bracketed references to entries . But you have a rich choice of presentation of the bibliography table through a customisation similar to the one for TOC or index. Each item in this table can be assigned a character style (allowing to bold or italicise individual items).