Create Custom New Edit and Display form for sharepoint list

You can use SharePoint Designer, InfoPath or some paid tool like Nintex, SPForm to customize the default list forms.

The best and simple will be using SharePoint Designer. You can create your custom forms for lists using SPD.

For more reference please refer here https://support.office.com/en-us/article/create-a-custom-list-form-using-sharepoint-designer-917d8fdb-ee00-4441-adb3-a94612d1d105

Let me know if you still didn't get what you want.

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Chanakya Jayabalan8y ago

You can create SharePoint hosted apps and insert them in to the new/edit/dispaly forms.

Let us know what you exactly require & what problem you are facing?

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Nanddeep Nachan8y ago

In SP Online, forms creation using SharePoint Designer and InfoPath is more simpler.

In SharePoint online, you cannot host your custom dll.

You may create Provider hosted App and have your custom logic in it using CSOM.

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