I would suggest
"also during the workshop"
Meaning: "from the beginning to the end..." cambridge
You will need to rewrite part of your sentence for the change in word forms, something like this: -
Given your recent comments, I think this would work best: -
The author is greatly indebted to ... and ... for suggesting this problem and providing several valuable comments. The author is especially grateful for the many enlightening discussions (during the workshop) which facilitated the emergence of several key ideas.
What I have done:
I have made the passage into two sentences as I felt it was getting rather long. I have used the word 'especially' which is used to single out a key thing above all others (in this case, from your comments the sense I gain is that the workshop and the ideas that came out of it were especially valuable). I have said that the ideas were facilitated by the discussions which I think is a truer reflection of what you were intending to say.
I have moved away from the concept of quantifying the ideas relative to the whole number of ideas, and instead focussed on the significance that the 'quality' of the ideas brought to you. I hope I have understood you well, from the question and your comments. I think the above works quite well.
Do Let me know if you have any questions or if I have made any incorrect assumptions.