Comment 31 for bug 1573031

As the suggested functionality in comment 3 is likely to be left for implementation with the notebookbar, the single toolbar mode UNO command should be a toggle/checkbox command that when toggled on enables (i.e. Visible=true)

View > Toolbars > Standard (Single Mode)

and disables (i.e. Visible=false)

View > Toolbars > Standard
View > Toolbars > Formatting
View > Toolbars > Image
View > Toolbars > Drawing Object Properties
View > Toolbars > Frame (Writer)
View > Toolbars > Table (Writer)
View > Toolbars > Bullets and Numbering (Writer)
View > Toolbars > Text Object (Writer)
View > Toolbars > Text Formatting (Calc)

When the single toolbar mode UNO command is toggle off, it does the reverse.