To create new conditions, just create a new or change an already existing alert policy. Press the “Add Condition” button in the headline to add a new condition with the desired event parameter, type of condition and value to match.
To link already linked conditions you have to select them all, i.e. in the example below you have to select the two “AND” conditions as well as all sub-conditions to their right.
This allows you to create most complex conditions in order to filter event data.