Dat file location can be defined using below configuration variables;

OVERHEADLINE_SICAT_SETTINGSDIR_DIR       = $(CIVIL_ORGANIZATION_STANDARDS)Overheadline/
OVERHEADLINE_SICAT_WORKSPACEDIR_DIR      = $(CIVIL_ORGANIZATION_STANDARDS)Overheadline/
OVERHEADLINE_SICAT_WORKSETDIR_DIR        = $(CIVIL_ORGANIZATION_STANDARDS)Overheadline/

by default these variables are defined in the following configuration file (for metric workspace);

C:\ProgramData\Bentley\OpenRail Overhead Line Designer CE\Configuration\Organization-Civil\_Civil Default Standards - Metric.cfg

You can learn more about workspace setup for OpenX products below;

https://bentleysystems.service-now.com/community?id=kb_article_view&sysparm_article=KB0020081

Example

Change Dat file location to D drive ProjectConfiguration folder;

OVERHEADLINE_SICAT_SETTINGSDIR_DIR       = D:/ProjectConfiguration/
OVERHEADLINE_SICAT_WORKSPACEDIR_DIR      = D:/ProjectConfiguration/
OVERHEADLINE_SICAT_WORKSETDIR_DIR        = D:/ProjectConfiguration/