I needed to insert timestamps into various interviews we transcribe, so I Googled this topic and came up with a wide variety of people trying to write Word macros and various work-arounds (such as typing CRTL+T, ALT+TAB, CTRL+V, ALT+TAB, etc.) to insert time stamps.
However, I found the easiest way was already built into Express Scribe.
To insert timestamps into a Word document, in Express Scribe go to Settings, then select Pedals and Hot Keys. Click Add at the bottom of the box to create a System-wide Hot Key. A Window pops up asking you to press a key. In my version of Express Scribe F1 and F11 are free. I chose F1. Then a Select Command box pops up. Scroll down to Copy Time and select this.
Now, as you play the audio file in Express Scribe, all you have to do is press your Hot Key (F1 for me) at the point where you hear the word you want to time stamp, and then CTRL V to paste it in Word.
Bingo. Two keystrokes and you're pasting timestamps! And it's a system-wide hot key, so you can insert timestamps into anything.