Like this: Highlight the text you wish to quote by dragging your mouse. As you release the button, the options pop up. I clicked “Quote” and it opened the reply box and I started typing “Like this…”
You can switch to another Topic in the top pane whilst still keeping the reply/contribution you’re typing in the bottom pane, and then quote again, still from the top pane, e.g.
Is this what you’re trying to achieve?
@Old_Scientist
Or this is what I sometimes do: start a new paragraph with an “@mention”. and start typing the user’s name. The system pops up a list of matching users for you to select from. It’s then clear who you’re addressing the next part to.