This functionality makes it possible to automatically link records according to a given MySql query. This type of action  is available if the entity has a field type "Related Items".

In the “Condition” option, specify the conditions for selecting and linking records. In square brackets, we can use the values from the current record.

e.field_171=[213] - a simple comparison of values

FROM_UNIXTIME(e.field_176,'%Y-%m')=FROM_UNIXTIME([214],'%Y-%m') - compare dates

e.field_169 in (50,66,44)  - list of values

e.parent_item_id = [parent_item_id] - compare the parent record