Loading Catalog Item variables of type Lookup Select Box can take a long time to pull up the drop-down options for the variable.
For variables that pull up data from Choice (sys_choice) table, if the variable type is set up as a Lookup Select Box instead of Select Box, the system runs a direct query on the entire sys_choice table and queries ALL the records in the sys_choice table instead of just the related table and field
Set the Variable type to Select Box, which provides the ability to point to the specific choice table and choice field, thus keeping the query narrowed down to just the needed data. For example, if the Select Box needs to display the incident.Priority field’s choice options, specify the choice table as Incident and the choice field as Priority
For more information, see the product documentation topic Variable types.