here is a quick tutorial for multi quoting.
first select the items you want to quote and click the multi quote button on each of them:

note multiquote is selected on these 3 responses
next select add reply at the top left of the screen (although you should also be able to just select regular quote in the las of the responses you want to quote):

the correct button to click is circled in red in the above pic.
add your response:

notice in the below pic that it has been posted and the multi quote as well as the respnse are there and are circled red in the pic. you can go to the section mentioned in this tutorial and see my replay with multiquote tutorial

notice the response circled in red in the above pic, also notice that the response will be in the library under Freshwater, Lake Malawi, Placidochromis sp. ‘jalo’? i am going to post this there so you all can see the multi quote from this tutorial.
that is it, very simple.