For a document library ,while checking in document, I need to open a customized check in form on click of check in button instead of opening inbuilt form.
Does anybody know how to do this ?
If i'm not wrong the Check-in button is a custom action. I suggest to look how publishing feature changes navigation links in site settings page. By default there are two links - one for the Quick Launch Navigation and second for the Top Navigation, but after activation of publishing feature you can see only one link - navigation. After research you can find out that this feature simply uses HideCustomAction functionality and adds a new custom action functionality to change links. I hope you can use this approach to solve your issue.