Custom buttons are not appearing in UCI

Microsoft have updated the Unified Interface’s UI with big improvements to the Sitemap and Command bar.

I have been facing this issue in unified interface, I did a lot of research on this and followed the below steps to resolve

We first need to get the organization id, this can be found in Settings > Customization's -> Developer Resources

or type the below command in Console

//Xrm.Utility.getGlobalContext().organizationSettings;

Xrm.Utility.getGlobalContext().organizationSettings.organizationId;

Open CRM Instance -- > Press F12 --> Console (execute the below scripts)

Xrm.WebApi.online.updateRecord("organization","{ORGANIZATIONID}", {"clientfeatureset":'<clientfeatures><clientfeature xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-Instance\"><name>FCB.ShellRefresh</name><value>true</value><location>Organization</location></clientfeature></clientfeatures>'})

Xrm.WebApi.online.updateRecord("organization", "{ORGANIZATIONID}", 

{'clientfeatureset':'<clientfeatures><clientfeature xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-Instance\"><name>FCB.DashboardCustomizableRibbon</name><value>true</value></clientfeature></clientfeatures>'})

Before executing Script

After executing the above script in Console window, we can see the button

E = "FCB.Client.Chart.DrillDown"

W = "FCB.DashboardCustomizableRibbon"

P = "FCB.DisableEditableGridControlOnPhone"

T = "FCB.LookupService"

N = "FCB.LookupQuickFind"

That’s it , your custom buttons will be available now in UCI.