I think it's crazy that HubSpot doesn't allow you to embed a form you have already made into a popup.
The popup forms themselves only allow you to input 4 fields and the forms we have on our site have quite a few more.
I think HubSpot should be able to have an ability to natively embed a form you have already created into a popup rather than having to use a third party tool like OptinMonster.
We appreciate your feedback! As you mentioned, pop-up forms allow you to add up to 4 fields, if you would like to add more, you would need to use a regular form.
I do see how the additional options in pop-up forms would be useful, therefore I would like to encourage you to post this as a product idea in our Ideas forum. The HubSpot Ideas Forum is a place for HubSpot users to discuss feature requests with each other and the HubSpot Product Team. We want you to tell us what features you'd like built! I found a product idea with a similar use case, but you can also create a new post. You can check the Ideas Forum Users' Guide here. Thank you!