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As Vahid notes, you can embed variables into Power BI reports using parameters. The below article is where I started learning about the concept.
Additionally if you want your parameter values to be referenced instead in the PBI model/DAX calcs you need to right-click "Enable Load" the parameter query in Power Query Editor which will load it into the report model for creating relationships and/or referencing in calcs.
https://powerbi.microsoft.com/en-us/blog/deep-dive-into-query-parameters-and-power-bi-templates/