Use case or problem
Right now the only way to make a blockquote of multiline text is to add > to the beginning of every line by hand. Needless to say, this is a time-consuming process.
Proposed solution
When multiline text is selected and > is entered, add > to the beginning of every line of the given text.
Related
Paste multiple paragraphs into block quote
The extension featured in the link above currently does not work. At least not for me.