Qrew LegendYou cannot do that directly, but suppose you are trying to protect your customer list. You can take away the user's ability to view the Customer table and instead provide a link to a report where the user need to say provide the first three characters of the customer name and have the report match on that value in an <ask the user> report targeting a formula field.
You would also need to take away the user's ability to create or modify reports
Mark is correct, outside of the REST API you can't limit what shows in a report. An alternative though depending on how 'secure' you need this to be would be to hide the save as spreadsheet icon from a table using the Security role setting to remove it from the UI. In its place you could put designated reports on a Dashboard that you could control to only allow them to download specific subsets, such as only downloading the 'Active' Customer list or something like that. You can append &dtla=xs to the end of any report to make the 'link' an automatic download from a Dashboard as another way that they can only download a report/list that you set for them. The issue remains that you still can't directly influence how many records are in the report you make outside of the filters, but an option.
