Hi @Kamil_Biela, welcome to the community 
I am afraid from checking the Notion documentation it seems the button creation is no longer supported through their API:
As of March 27, 2023 creation of template blocks will no longer be supported.
Template blocks represent template buttons in the Notion UI.
Other blocks not supported by n8n’s Notion node can be created through the HTTP Request as suggested here, but I don’t think there’s a way to achieve this for buttons (or at least I couldn’t find one).