You may be wondering about the limit Salesforce put while creating lightning page using Lightning App Builder. You can create three types of page in Lightning i.e Home Page, Record Page and App Page. Whenever you are going to create them, You have the ability to select the layout structure of the Page.
Once you have selected a layout with you want to proceed further, You can add Components in the section. For e.g If you have selected Region as Header and Left Sidebar, you have three section where you can put your components. The question here is how many components you can add in each of three section on your lightning page?
Salesforce allows 25 components to be accommodated in each of the section you have in your Lightning App Builder Canvas. So, If you have selected Header and Left Sidebar as page region, You cannot add more than 75 component on your page.
We all know, in very rare scenario, We have to add more than 75 components on a single Page. Also, it is not advised to have that much component on your page because of page performance issue.
What should i do if i have to accommodate more than 25 components in Header section of the Lightning Page?
You have to create custom page layout using Custom Lightning Component. Every standard Lightning page is associated with a default template component, which defines the page’s regions and what components the page includes. Custom Lightning page template components let you create page templates to fit your business needs with the structure and components that you define. Once implemented, your custom template is available in the Lightning App Builder’s new page wizard for your page creators to use.
Custom Lightning page template components are supported for record pages, app pages, and Home pages. Each page type has a different interface that the template component must implement.
Find a Working Example here:- Create a Custom Lightning Page Template Component