You can use the NITRO Utility to both remove Custom Actions from the list ribbon and also to add your own script to web pages within the site.
Also, NITRO Utility can be used to edit and remove NITRO forms configured on lists in current site.
Manage list level user custom actions: First, click the "Go" button to get to the custom action settings interface:
From here you can disable the buttons for both Custom Actions and custom built script buttons from the selected List. Use the "X" under Actions to remove the button from the item's and list's ribbon interface.
If you need to add in a script to load on every page, you can use the "Add Web Script Link" section to add in your own custom script.
Configured NITRO forms: First, click the "Go" button to get to the NITRO forms settings interface:
It will navigate you to the below page
here you can edit, export the NITRO form configured on lists in current site.