If you want to get values from another record, you have to select with a individual condition, you should use this block. This block could be used to execute every Expression you could create in the context of this other record. This means all simple variables you could access ($id, $name, …) are loaded from the matched record. Because of the condition, there could be also found multiple records. The expression will be executed for every record, independently.
You also could limit the number of result records and sort the records to only get the latest ones.
A special function is, how the environmental variable $env will be handled, because they are also available inside the custom expression. And every modification you do on this variable will be transferred back to the main workfflow. With this transmission you could collect records in your vtiger, if you simple add every record to an $env variable.
If the task couldn't found any records match the condition in the selected module, the second “do not exist” output will be taken.
In this way you could get values from a single field of this record or save the ID for later use.
$env["external_recordid"] = $id;
Because of the freely configurable conditions, the Performance could be heavily slower. This block create database queries and directly translate the conditions in this query. If you use this block for lots of operations, like the new Import Feature, you should ask your system administrator to set database indexes on the columns you filter. This will heavily speed up the Process.