is it possible to create a custom controls in sharepoint office 365

SharePoint add-ins cannot be compared with custom controls though the question is quiet open about what needs to be achieved with custom controls.

Hi Parthasarathy,

 

I hope you are expecting to change or add to the modern pages. If so, yes you can use SharePoint Framework extensions to extend the modern pages. Check below link.  

 

https://docs.microsoft.com/en-us/sharepoint/dev/spfx/extensions/overview-extensions