MSSQL Express exclussion on global level

You would either:

Add an exclusion to the AppliesTo based on some property that is unique to the MSSQL express server. This would exclude all instances on that device.

Or add a discovery filter that excludes just the MSSQL Express instances. This would allow regular MSSQL instances on the server to be discovered and monitored, while excluding the express instances.

The exact details on how to do that will depend on which method and what unique property you can find to programmatically distinguish between regular MSSQL and MSSQL express.