pgagent on linux

Dear support team

I am trying to install and run pgagent locally on linux mint 19.1 with postgresql 11 and pgadmin4.
I added the extension to my database, the schema pgagent was created.
In the tree view of pgadmin "pgagent Jobs" did not appear.
After some attempts to start pgagent manually via pgagent <connectstring> "pgagent Jobs" appeared.
I created a job, schedule, steps to write something into a table of this database, and it worked.
But: the job and the jobsteps where NOT persisted in the tables in the schema pgagent, these remained empty.
Schema pgagent is notabene visible in Navicat, NOT in pgadmin.
I created another job via sql in the database (using Navicat). This hob worked, too.
I need to be able to manipulate my schedules as well from pgadmin as from the database.
A colleague of mine installed pgagent on WIndows and showed me the jobs written in the postgresql database.

What was my mistake?
Any help is highly appreciated.
Best regards, Elke Hofmann