Hi,
I think it will be a nice idea to have a revision cloud tool. Something easy will be fine, something like to draw a circle or a rectangle but you get a cloud.
It will be wonderfull create at the same time a tag 
Here’s an oldie:
SketchUp Plugins | PluginStore | SketchUcation
[Plugin] RevCloud v1.1 • sketchUcation • 1
It doesn’t add a tag but you can easily attach a text-note to it…
TIG, thanks you and sorry. I did wrong. I wanted to ask for LAYOUT! I think the featere is needed in Layout.
You could make revision cloud elements with text and add them to the scrapbook.