SharePoint Online: Save List as Template Missing?

Problem:  "Save List as Template" is missing in SharePoint Online modern sites!

Root Cause: "Custom script" feature is disabled!

Solution: Enable Custom Scripting at SharePoint Admin Center and Site Collection Levels.

How to Enable Custom Script in SharePoint Online?
To allow custom script in SharePoint Online, follow these steps:

• Sign in to Office 365 and go to the SharePoint Online Admin Center.
• Click on Settings from the left navigation >> Scroll down to "Custom Script" section
• Under Custom Script section, Set "Allow users to run custom script on personal site" and "Allow users to run custom script on self-service created sites" options. 
  
• Click on "OK" to save your changes.

This enables custom script in SharePoint Online. However, this change may take up to 24 Hours to reflect. To enable scripting on a particular site collection immediately, use this PowerShell script through SharePoint Online Management Shell.

Enable Custom Scripting at Site Collection Level:

#Variables for Admin Center & Site Collection URL
$AdminCenterURL = "https://crescent-admin.sharepoint.com/"
$SiteURL="https://crescent.sharepoint.com/Sites/marketing"

#Connect to SharePoint Online
Connect-SPOService -url $AdminCenterURL -Credential (Get-Credential)

#Disable DenyAddAndCustomizePages Flag
Set-SPOSite $SiteURL -DenyAddAndCustomizePages $False

This fixes the save list as template not available issue in SharePoint Online!