Custom views with view designer are migrating to Azure Monitor workbooks

Azure Monitor is making changes to the custom views experience in Log Analytics Workspaces. Beginning March 2020, we will be replacing the View Designer tool with Azure Monitor Workbooks. Workbooks provide a flexible canvas for data analysis and the creation of rich visual reports within the Azure portal. They allow you to tap into multiple data sources from across Azure and combine them into unified interactive experiences.
Source: Azure Roadmap