How to create a button in top toolbar in mobile?

Hi PDFTron,
I wanna create a button on top toolbar in mobile. How to make it in React Native language?
Thank you!

Hello, I’m Ron, an automated tech support bot :robot:

While you wait for one of our customer support representatives to get back to you, please check out some of these documentation pages:

Guides:APIs:Forums:

Hi,

Thanks for contacting us. Could you give us a high level use case of what you’re trying to achieve here? What kind of buttons are you trying to add here and what functionality does it provide?

Thanks,
Andrew

Hi Andrew,
I just wanna create a button next to vertical 3 dots icon. When click the button, the document will be saved on my server. I use React Native language.
Can you give me the solution how to make it?
Thank you!