Hi,
Tags information is not available in Log Analytics data by default or trough some of the built-in ingestions. Because of that there is no way to create computer group based on tags. You could potentially create some automation workflow (Azure Automation, Functions or Logic apps) which gets VM and tags data from Resource Graph and feed that data periodically to Log Analytics or directly update the query of the Kusto query behind the Computer group. In the first scenario you will use the data to create the query for Computer group, in the latter you will update the query with some static values to include the VMs in the query.
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