If the extra attribute that you wish to add can be returned from a sql query then there is an easy way to do this.
For example this is the Aggregate Filter query that returns the extra attribute 'vsmtolp'
SELECT
aggr.name,
node.name AS 'node.name',
cluster.primary_address AS 'node.cluster.primary_address' ,
aggr.available_size_mb,
1 AS 'vsmtolp'
FROM
cm_storage.aggregate AS aggr
JOIN
cm_storage.node AS node
ON aggr.node_id=node.id
JOIN
cm_storage.cluster AS cluster
ON node.cluster_id =cluster.id
WHERE
aggr.block_type = '${block_type}'
You can now create a Finder using this filter and add the attribute 'vsmtolp' as a return attribute for the finder. After you have done this it should be possible for you to use the expression "aggregate1.vsmtolp == 1" in the advanced tab of another command