Reverse, Invert and Silence Effects are greyed out on Audition

I have to say.  As someone who is very familiar with Audition's base template software, that being the original Cool Edit Pro, released by Syntrillium Software, I find this HIGHLY inconvenient.  In that original software you had the ability to add silence to any location of the wave file, including the very tail-end of the wave file.  This is ESSENTIAL for basic audio production... like, "bare-bones" essential.  For example, right now I am needing to add about 1.5 seconds of silence to the very end of a wave file so that there is a buffer of space between the previous wave form and the one I was needing to insert.  I can not have each wave file "back to back" because I plan to do both delay and enveloping effects over the entire comp and so "back to back" spacing these waveforms will not work for this particular effect.  The fact that Adobe has removed this feature for some reason is concerning.  If what you are saying is true, then in my mind this makes Audition inferior to it's predecessor... which is unacceptable.  So, I must ask for the sake of pure, clarity... is the ability to add silence to the very end of a waveform not possible in Adobe Audition as it verymuch was in Cool Edit Pro?  Please let me know so that I may stop wasting my time with this software and switch to one that is more capable.