Hey Jagadeesh,
There is not index.html in the mendix 9.x version in the mendix codebase which you can modify. That's why,
You cannot make changes in index.html page as it's in deployment directory so every time we start the server it's getting overwritten.
pls refer to this question below,
https://forum.mendix.com/link/questions/118912
There I told, how to edit your index.html.
And for SAML, pls refer to the documentation,
https://docs.mendix.com/appstore/modules/saml/#ssolandingpage
Hope it helps!
You are mixing stuff up here. The deeplink loginconstant has nothing to do with the SAML setup. Did you follow the steps as described here: https://docs.mendix.com/appstore/modules/saml/#ssolandingpage ?
Could you otherwise edit your question and show us the content of your index.html?
Regards,
Ronald