Do Jehovah Witnesses believe that Jesus Christ returned to Earth in 1914, or has this teaching now been abandoned? I would be interested in having some clarification on this topic.
I once had a poster displayed in my house with the text, "The coming of the Lord draws near." James 5:8. Two very sincere and concerned Jehovah Witnesses knocked on my door and explained you can't say that (James 5:8) as it already happened in 1914. I am informed that this is a doctrine that has now been abandoned or revised. I am curious as to which is true?
Jehovah's Witnesses do not believe Jesus returned to Earth in 1914. Rather, they believe Jesus began ruling from Heaven in 1914. There haven't been any adjustments regarding 1914 in recent years.

The significance of 1914 is pretty well known among all JWs. It marks the beginning of Jesus' kingship in heaven over God's Kingdom. The book, What Does the Bible Really Teach? says:


  At that time, “the appointed times of the nations” ended, and Jesus
  Christ was installed as God’s heavenly King. —Psalm 2:1-6; Daniel
  7:13, 14.
  
  Just as Jesus predicted, his “presence” as heavenly King has been
  marked by dramatic world developments​—war, famine, earthquakes,
  pestilences. (Matthew 24:3-8; Luke 21:11) Such developments bear
  powerful testimony to the fact that 1914 indeed marked the birth of
  God’s heavenly Kingdom and the beginning of “the last days” of this
  present wicked system of things.​—2 Timothy 3:1-5.


This book is used very commonly to aid in conducting Bible studies, so you can be sure that these are the current beliefs of Jehovah's Witnesses.

In regard to James 5:8, this "coming" is discussed in more detail at  Matthew 24:3-14. It's clear from this scripture that it represents a period of time, not a single event. The word translated as "coming" is also commonly translated as "presence".

In regard to your comment which mentions that "every eye shall see him" (Revelation 1:7), Jehovah's Witnesses believe there will be a supernatural sign of Jesus' presence as well. It's described in Matthew 24:30 as an event that will occur very shortly before Armageddon. This is an event that didn't occur in 1914. It's still in the future.

For more information see: What Is the Coming of Christ?