There is this Look and Feel option in every portlet settings:

I want to create hook for this tab. Which JSP file do I have to override? How can I add my custom field in this tab (like Use Custom Title)?
There is this Look and Feel option in every portlet settings:

I want to create hook for this tab. Which JSP file do I have to override? How can I add my custom field in this tab (like Use Custom Title)?
How to find such files:
Look into
src/content/Language.propertiesfor a term from your screen with high significance, e.g.Use Custom Title:Now search for a file that contains the key, in our case
use-custom-title:That is indeed the file you are looking for.