Systems and methods are provided for enhanced alert generation based on real-time manipulation of datasets. An example method includes accessing datasets including a plurality of rows each indicating a plurality of values. Occurrences of alert definitions are monitored via applying the alert definitions to the datasets, the alert definitions specifying expressions utilizing one or more of the values, with an occurrence of an alert definition indicating satisfaction of the specified expression and causing an associated alert to be generated for evaluation. Presentation of an interactive user interface associated with customizing alert definitions is caused. The interactive user interface presents a first visual portion, the first visual portion enabling specification of an expression for a customized alert definition. The interactive user interface presents a second visual portion, the second visual portion comparing occurrences of an existing alert definition with occurrences of a customized alert definition specified in the first visual portion.