Please, consider using expandable/collapsible sub-options to save menu space. 
This is the easiest approach. No wonder that recently it was implemented in some new tools in Rhino 9 WIP, so the code is already there and you just have to apply it to other tools with tall pop-up windows. The Rhino Options panel uses a similar approach since many years.
You can either use arrows to expand the sub-options, or simply click on the name of the sub-option to expand it or shrink it. It’s described in this proposal here:
I guess that most users will not need the “Sizes” option (scale), as well as a few others, so being able to set the menu at a minimum size (and remember the state during the session, unless it’s changed by the user again) will leave more viewport space.
