Hi,

For adding an extra field in tree view via the user interface. first, you have to activate developer mode.

Then go to Project -> Search -> Tasks, click on "List" icon

Then go to developer option in the top of the screen

    This option is seen only when you activate the developer mode.

From Developer Option, Select Edit Tree View

Then you will get an option to edit the tree view.

Add here an extra field tag_ids. Save the changes. Go back to tree view

Then Refresh the Page. You will get the new field in tree view

Thank you