Error: identifier is too long, how do I change the schema name in the database?

I am trying to run a query where I specify the name of the schema where my tables are located, which results in the error of: identifier too long

How can I rename my schema permanently, without causing harm to the integrity of the database?

If you’re talking about schemas in the database that Survey Solutions creates then DON’T - don’t rename or otherwise modify anything in that database without wanting to intentionally corrupt your setup and/or lose data.

The database and all objects in it are managed by the application and expected to be intact. You should export collected data via gui/api and work with that copy.