The seminars feature guest speakers and case-study presentations on how key issues or challenges have been handled by others in the field. 同意楼上一位的说法guest speakers 和case-study presentations 并列关系, feature 为谓语,on后面是case-study presentations 的修饰语了。翻译成什么样并不重要,只要意思理解对就好了
The seminars(主语) feature(动词,做谓语) guest speakers(宾语1) and case-study presentations(宾语2) on how key issues or challenges have been handled by others in the field.(on后面全部是用来补充说明presentations的)