Hi.
Anyone done any work on this yet?
It's May 2021.
I just got this pop up on my brand new subscription to SU Pro 2021:

@unknownuser said:

Error Loading File #FlattenToPlane.rb
Error: #<LoadError: cannot load such file -- #WorkPlane.rb>
C:/Program Files/SketchUp/SketchUp 2021/Tools/RubyStdLib/rubygems/core_ext/kernel_require.rb:92:in require' C:/Program Files/SketchUp/SketchUp 2021/Tools/RubyStdLib/rubygems/core_ext/kernel_require.rb:92:in require'
C:/Users/jenni/AppData/Roaming/SketchUp/SketchUp 2021/SketchUp/Plugins/#FlattenToPlane.rb:51:in `<top (required)>'

This plugin would be super useful to me.
But, if your life has taken a different turn, I understand.
Bless you and have a good one.
~Ww