Actually you can - just simply click anywhere empty and then click 'paste'.
Please explain a little more
Instead of inserting comments with excerpt(if you tell me this, i know already )
Inserting into the document.
Oh! Sorry, I thought you were referring to adding images to Mindmaps.
For the documents - sorry we currently do not support this function.
This is indeed quite frustrating - I have reported this to our developer team.
Hopefully we could support this in the future.