is it possible to…

Hi there,

is it possible do easily add new fields for the job ad ? I mean not using code.

You can use this tutorial – https://wpjobmanager.com/document/editing-job-submission-fields/ – to achieve what you need.

Another way to add new fields would be to use a third-party plugin that you mentioned.

is it possible to create a specific page that will display all the ads of a certain category ? Second question I think is a yes too:
https://wpjobmanager.com/document/shortcode-reference/

Correct! You can use the categories argument in the [jobs] to achieve what you need.

Cheers,
Davor