HTML Content
Untouched editor HTML. Bootstrap never rewrites this output.
SafetyHQ Form.io Workbench
Build the content in TinyMCE first, then apply Bootstrap classes separately for Form.io's Custom CSS Class field. The HTML output is never modified by the Bootstrap selections.
Copy the HTML into Display > Content and the Bootstrap string into Display > Custom CSS Class.
Untouched editor HTML. Bootstrap never rewrites this output.
Paste this into the Form.io HTML element's custom CSS class field.
Themes save only the Bootstrap selection. Snapshots save the editor HTML and the Bootstrap selection together.