You can modify and increase the track_activity_query_size parameter value which controls the length of the query, it postgres server side setting, you can check postgres documentation for more information.
I'm using pgadmin 4.21, following Server Activity and drilling into individual requests, looking at SQL for certain requests. The SQL is limited to 1024 characters, but that's cutting off the where clause, which I need to see. I was able to find a solution for this for older versions of pgadmin, but am unable to see the whole SQL in pgadmin4. How do I see the whole query?