I have a requirement to create multiple(around 100) custom permissions. Can this be done using data loader or workbench? In data loader when we select insert option I don't see custom permissions object. This object is available if we select export in data loader
Custom Permissions are a type of metadata, so you need to use CustomPermission to create them. Probably the easiest way to do this would be a NodeJS/Python/etc script to output all of the files you need, then use Salesforce DX to deploy (though you could also use workbench at this point).