Hi Victor,

I've tested this on a V12 and V13 instance and you're right. I consider this a bug in the framework. You should be able to add as many records as you'd like just like anywhere else in Odoo.The issue seems to be related with the widget  many2many_tags_email which is set on the field that you're referring to.I've reported this problem to Odoo at https://github.com/odoo/odoo/issues/38658

In the meanwhile you can workaround this issue by modifying the view. Activate developer mode, open up the wizard that asks you for the email invites and then click on the developer icon to open the view. In this view you'll see a line with the code "<field name="partner_ids" invisible="context.get('survey_resent_token')" widget="many2many_tags_email" placeholder="Add existing contacts..." context="{'force_email':True, 'show_email':True}"/>". Change the widget from "many2many_tags_email" to "many2many_tags" and save your view. Reload your view and you'll now be able to add more than 40 records. See this image for more details.

Regards,
Yenthe