QGIS expression: select from

I have a project file with many nested layers and would like to query certain layers without having to click on them first. The expression tool however requires me to select the layer I want to query. Is there a way to do an expression like SELECT FROM 'Layername'="Cities" WHERE "CITY"='New York' AND "Pollution" = 'low'?

I dug around a bit and only found the Expressions+ plugin but that didn't help either.