Currently you cannot filter your columns in Embeddable, however you can have the columns show a blank result for certain customers - this really only makes sense in a table component, for example.
If you want to ensure certain customers do not have access to certain columns (i.e. column-level security instead of row-level security), the best way to do this is to create 2 Embeddables, one with the data you don’t want to use hidden, and then to surface the correct Embeddable on your UI depending on the customer.
This works best because alternatively, the customers who don’t have access would see charts with ‘no results’ due to not having access to the dimensions (columns) required to populate the chart data.