I was able to figure out answers for all of my questions from my previous post above by looking at the array structure for the toolbars provided in the documentation for the toolbars filter. Thanks again for providing the detailed information in this documentation which allowed me to answer my questions about modifying the toolbars.
For those who might need a similar solution, here are the answers to my questions:
1. The special character button can be added in the same manner as the bold, italic, underline buttons as outlined in the documentation. Just add “charmap” to the array.
2. Similarly the paste as text button can be added in the same manner as outlined in the documentation. Just add “pasteastext” to the array.
3. Additional buttons can be added to the Basic toolbar simply by adding the code for the button to the end of the array for the row in the toolbar you want to add the button to. For example to add the special character button to the first row of buttons for the Basic toolbar:
$toolbars['Basic' ][1][] = 'charmap';
4. Data is not lost when editing the toolbar options, whether adding a new toolbar or modifying an existing toolbar.
Thanks again for the excellent documentation provided here on the ACF site!
