Hi Purna,
There are certain restrictions in GUI about such addition. The same goes for FW hosts also. Can you try adding the CA certificate from CLI. You can use the below format
conf t
ssl
inline ca-certificate NAME_of_CA_Cert "end-701654422-inline"
<<Insert the CA cert here>>
end-701654422-inline
exit
Also to add the new CA cert to "browser-trusted" CCL, use below
edit ccl browser-trusted
add NAME_of_CA_Cert
exit