Configuring pg_admin 9.6 while there are users using it on Windows Server 20XX? I read something about pg_ctl reload (I'm not sure if that's on the Windows distro of pg)...also is there a way to verify the configuration isn't going to break it completely, like apachectl configtest?
I don't think that there is anything like that for PostgreSQL.

pg_ctl reload does check the syntax of the config file, but it only works with a running server.  If there is a syntax error it does report it, but it reports it to the running server's log file, not to the command line.

And if there is no syntax error, then it applies those changes which it can apply to the running server, which doesn't seem like what you want.

Some settings cannot be changed with a reload, but only a full restart.  Changings to those setting will be noted in the log file and then ignored.  Other things are called errors, but not syntax errors.  Those things will also get reported to the log file and ignored.  But these conditions won't block other changes from getting applied to the running server.

If you change "shared_buffer=1TB", that is valid syntax and valid semantics, so you wouldn't get a warning on that front if you tried to reload it.  But it also wouldn't apply the change, as shared_buffers can't be changed without a full restart.  Then if you tried to do the restart, your server would stop and then fail to start again, because your server (probably) doesn't have 1TB memory available to it.



Your comment asks specifically about adding users. That is a bit of a different topic than I had in mind.  In PostgreSQL, you can add users via SQL alone as long as they match to a pattern already existing in the pg_hba.conf.  If you do need to change the pg_hba.conf (to add hosts, or to tie specific hosts to specific users), that does require a reload, which can also be done in SQL via SELECT pg_reload_conf();.  The pg_hba.conf file is quite a bit simpler than the postgresql.conf file.  But there is still no "lint" like tool for it, that I know of. It never needs a restart to take effect (unless you change it to invoke new modules like ssl that themselves are not set up yet and need a restart to set up).  It only needs a reload.  If you introduce syntax errors to pg_hba.conf, then the reload will leave things alone, and complain to the log file.  If you were not paying attention to those complaints and issued a restart, you server would stop, and then refuse to start again due to the syntax errors in pg_hba.conf.  So good rules of thumb are to never issue a restart when a reload would suffice, and look in the log file after a reload.  Also, try to use wildcards to the extent feasible in the pg_hba.conf so that you can manager users via SQL rather than pg_hba.conf