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.properties
for a term from your screen with high significance, e.g. Use Custom Title
:
...
use-custom-title=Use Custom Title
...
Now search for a file that contains the key, in our case use-custom-title
:
portal-web/docroot/html/portlet/portlet_css/view.jsp
That is indeed the file you are looking for.