Multiselect lookup field in Dynamics

Question

Can I:

1. make manipulation with subgrid so I can choose multiple Contacts and save them in the field (or even better choose only the email address from the Contacts) or
2. make a lookup field to Contact that allows me to choose multiple contacts

Longer description of the problem:

• I have made some customization of the Invoice entity in Dynamics Sales, but what I also need is an email failed that is a lookup to Contacts, so I can choose a multiple contacts, so later on I can get the email information and send them an email with power automate. But since I'm new to Dynamics I'm not sure how to manipulate with the subgrid, I researched something about creating N:N relationship, but I'm not sure how can I manipulate with on save/ on load events, cause I need to choose multiple contacts and save them in this field. Customized Invoice Entity