-Slightly OT, why would you need plunge cut with a circular saw? I cannot think of a time that I have needed it in 25+ years of fixing and making stuff.
The very first time you lay a plunge cut saw down flat on a surface after making a cut & not worrying about a spinning blade, you'll wonder why you waited so long for this small convenience.
It's not really a planned feature of the plunge function, but, it's something you really miss when it's not there.
This is the cutting table I use.
http://www.thewoodshop.20m.com/panel_cutting_table.htm
With my saw, I usually end up laying the saw across the two narrower cross members while I move the plywood around after making a cut. Both the fully enclosed blade (made possible by the plunge) and the rather precarious place to place the saw make using a plngue saw much more steady than a conventional circular saw.
I also use that same table when using my circular saw with a shop made guide for things that a track can't lay flat on - - such as counter tops with a built in splash guard.
When I do that, I always end up bending down and putting the circular saw on the ground.
It really sounds like a ridiculously trivial thing, but, at my age and girth, the less bending down I do, the better off I am!
"Life is what happens to you while you're busy making other plans." - John Lennon