Custom tab icons and modal screen

1. Which 'tabs' are you referring to? Your question doesn't have enough information to pinpoint where exactly you want to customise some icons
2. As far as I know, not with the standard 'Related Action' on a Record. BUT: in 20.1 there is the new 'Record Action Field' which allows you to put Related Actions anywhere within your application and, yes, modal is an option.

I am talking about the Page tabs on site

What function we use for modal display?

Hello. You can configure icons on a page  when you create the page as part of the Site object:

Similarly, when you configure a related action shortcut as part of a record, you can choose whether it displays in a dialog box. 

Thank you! For the icons, can I upload custom icons?

sitwatn0001 said:

can I upload custom icons

No - related action icons use the (extensive) "Styled Icon" set, which is the same thing that's used for the Rich Text Icon component.

sitwatn0001 said:

can I upload custom icons

No - related action icons use the (extensive) "Styled Icon" set, which is the same thing that's used for the Rich Text Icon component.