While you could just click onto 1-40 / n and replace it manually with i.e. 1-999. This would change the number of lines of that list for as long as you are in that view.

If you want to set the number of lines as a default, you will need to find the view that was created by Odoo Studio and update it.
To do so, first enable the Developer Mode (https://www.odoo.com/documentation/18.0/applications/general/developer_mode.html), then navigate to the form view that holds the list view you've added. From here, click the Debug-icon on top right and click View: Form:

In this view, now go to the tab Inherited Views and find views named Odoo Studio: xyz (External ID: studio_customization.odoo_studio_xyz). In the following action window (pop-up), find your added field and its subsequently inherited <list/> node and add, i.e.

limit=999

as an attribute to that list:

Note: Above example is based on a custom Many2many field 'Country' added to the Contact form.