How to modify/design list form

Hi harishpatil,

I understand that you want to modify a SharePoint list form.
then you have three options

1) Lightweight using Json formatting

Take a look at this article:

https://learn.microsoft.com/en-us/sharepoint/dev/declarative-customization/list-form-configuration#configure-custom-body-with-one-or-more-sections
Using a custom form format you can re-structure the controls in your form into multiple sections.
This is not very powerfull, but easy to to.

2) Low Code with custom PowerApps Form

You can choose to customize the form using PowerApps

See more information about this here:
https://learn.microsoft.com/en-us/power-apps/maker/canvas-apps/customize-list-form

3) Development with an SPFX Form Customizer

If you want to use Javascript, then you need to use an SPFX Form Customizer. 
See more information here
https://learn.microsoft.com/en-us/sharepoint/dev/spfx/extensions/get-started/building-form-customizer and an example here
https://github.com/pnp/sp-dev-fx-extensions/tree/main/samples/react-formcustomizer-customers

You can rebuld your complete form the way you like it using a customizer.

Best Regards,
Sven