How to add Save Button to only Notes Tab in task edit.
Support Forum
The button placed outside of tabs, in the main panel, so you could try to initially hide that button, let's say in https://bryntum.com/products/gantt/docs/api/SchedulerPro/feature/TaskEdit#event-beforeTaskEditShow event handler, subscribe on tabPanel tab change event https://bryntum.com/products/gantt/docs/api/Core/widget/TabPanel#event-tabChange
and track activeItem
inside to update button visibility as you need.
Here you can find names of elements in tabEditor and some code snippets that help you with that https://bryntum.com/products/gantt/docs/guide/Gantt/customization/taskedit
All the best,
Alex