Thanks for the story. I'm aware that editing sash values is difficult for a beginner, and a graphical tool would be more handy than editing values with a text editor.
Please, understand that I'm more motivated to improve Sweet Home 3D than the Furniture Library Editor.

Sean's video about the Furniture Library Editor is nice except that editing a SH3F file stored in the folder where libraries are stored isn't a good idea, because it obliges you to relaunch Sweet Home 3D at each change. Importing a modified library stored elsewhere is faster that relaunching Sweet Home 3D and less error prone.