Using QuickOSM to select more values in key?

The QuickOSM plugin dialogue also has an option to use a query from the Overpass Turbo API.

http://overpass-turbo.eu/

Here I can construct a query to find amenities = bench and townhall using the wizard:

amenity = bench or amenity = townhall

The query runs and the results show, but the code to run this shows on the side:

/*
This has been generated by the overpass-turbo wizard.
The original search was:
“amenity = bench or amenity = townhall”
*/
[out:json][timeout:25];
// gather results
(
  // query part for: “amenity=bench”
  node["amenity"="bench"]({{bbox}});
  way["amenity"="bench"]({{bbox}});
  relation["amenity"="bench"]({{bbox}});
  // query part for: “amenity=townhall”
  node["amenity"="townhall"]({{bbox}});
  way["amenity"="townhall"]({{bbox}});
  relation["amenity"="townhall"]({{bbox}});
);
// print results
out body;
>;
out skel qt;

Simply copy and paste that query code into the Query pane in QuickOSM, then click Run Query:

If you don't get all the geometry types returning, open up the 'advanced' section to ensure all geometry types are set. At first all geometry types weren't returned. When I opened the 'advanced' tab - without changing anything - and ran the query again, all geometry types came back.

For future look outs: you are looking in the wrong place with your query. You want to query for buildings.

<osm-script output="xml" timeout="25">
    <id-query {{geocodeArea:Oldenburg, Germany}} into="area_0"/>
    <union>
        <query type="node">
            <has-kv k="building" v="hotel"/>
            <area-query from="area_0"/>
        </query>
        <query type="way">
            <has-kv k="building" v="hotel"/>
            <area-query from="area_0"/>
        </query>
        <query type="relation">
            <has-kv k="building" v="hotel"/>
            <area-query from="area_0"/>
        </query>
    </union>
    <union>
        <item/>
        <recurse type="down"/>
    </union>
    <print mode="body"/>
</osm-script>