“也许您认为他的编程经验不足”的英文是？

首先，“也许”是说我对对方想法的推测，而不是推测他可能经验不足。
其次，不足，用lack of experience比较好，用unexperienced也可以，但有些语气稍强。
第三，汉语用了您，讨论的又是工作，所以比较正式,要讲究礼貌和措辞。
因此，参考意见如下：
1.Perhaps you think that he lacks a little experience in programming.
2.Maybe you don't think that he is so experienced in programming.

He may be not,in your opinion, experienced enough in programming.