Flow is not triggered on file change event

Hi All!

I have the following configuration:
Nextcloud running from the official container: nextcloud:25.0.2-apache
Logging enabled in configuration to DEBUG: 'loglevel' => 0,
Installed Workflow external scripts v1.10.0

In the Administration settings > Flow I have the Run script workflow configured with the following settings:
a) When File created and File updated
b) and Filename matches : /^[a-zA-Z]*\.kdbx$/i
c) Run script: cp %n keepass_pyknix/$(basename %n).bak

So, basically what I want to achieve is: if <filename>.kdbx changes, copy it as new file intokeepass_pyknix/<filename>.kdbx.bak. Of course keepass_pyknix/ nextcloud folder/location is available.

The problem is that the Run script workflow is not triggered at all. I checked the logs. When I installed Files automated tagging app I was able to see in the logs that the tagging flow is triggered and the app name is "app":"workflowengine", e.g.

{"reqId":"NkCWyWJvDw1J5deIPuuI","level":0,"time":"2023-01-07T14:28:48+00:00","remoteAddr":"xxx.xxx.xxx.xxx","user":"xxx","app":"workflowengine","method":"PUT","url":"/remote.php/dav/files/xxx/keepass/.xxx.kdbx.1673101737901","message":"No flow configurations is going to run Automated tagging","userAgent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 12_6_1) AppleWebKit/537.36 (KHTML, like Gecko) KeeWeb/1.18.7 Chrome/89.0.4389.128 Electron/12.0.7

What I am doing wrong?
Additional thing, the workflow documentation (GitHub - nextcloud/workflow_script: Rule based processing of files through specified external scripts) says: After enabling this app, rules can be defined in the admin settings, "External scripts" section.. I can’t find “External scripts” section in my Nextcloud instance.

Thanks in advance for the help.