I want to know how can I change the default assigned group on the service operations workspace to show all task, incidents... related to my specific work group every time I open the workspace.
This isn't an easy answer, but let me explain a few things. For the SO Workspace there are 2 variants for home page. Audiences (roles) control which page you are routed too:
What you are showing is the Service Desk variant. The other variant shows Incidents, Problems, & Changes individually:
If it were me, and I'm pretty comfortable with UIB, I'd set the Service Desk variant audience to admin only. That way everyone is redirected to the Tier 2/3 page (variant).
Otherwise,
Option 1: If you really want to build your own page, you could add another variant and add data visualizations to the page, configured how you want.
Option 2: Those items shown on the Service Desk variant are built in UX Client Script includes (sys_ux_client_script_include). You could create overrides if you really wanted to change them but understand they build EVAM cards that display under the item you select. There is a lot more coding and changes needed to make the changes. Either way, you probably need to create a new variant. Doc Site
