Well, I am answering my own question. Haha.
Let me make an apology first - I did not know there is a separate board for user discussion forum than this Q&A (I thought this was such forum), so when I read all 100+ questions here (for StudioLIve Series iii) and found no questions or answers regarding additional effects, I went ahead and posted this question.
Yesterday I logged on to the user forum (thinking that was this Q&A board and wondering why user interface has changed over night), and I found that my posting was disappeared. Well, it wasn't. Now I know that I posted this question here, not there.
After the realization, I searched the user forum for this topic, and sure enough there already was a similar question asked and answered:
https://forums.presonus.com/viewtopic.php?f=338&t=22968&hilit=additional+effect
In summary, there is no additional effects which we can load to the mixer, but there will be some in the future. I am definitely looking forward to it!
Thank you!
