Can I auto collapse the Custom Forms in the Project Details section on a project?

There isn't, but…

You can set display logic to display sections and/or fields that aren't needed based on what you choose in a control field. It's bit of a hack but if you create a radio button field called "Show Widget Section" and then only display the Widget section when that "yes" button is clicked, you can achieve the same thing.

Oh I found it in the top right corner there is a little icon for it.

Side question - is there any way to collapse sections within a custom form?

Our forms can get very long and when we need to access a section that is toward the bottom of the form we need to scroll quite a bit. It would be great if we can collapse the sections to only see the section headers and only expand the section we are looking for.

Mine collapse automatically. I kinda wish I could un-collapse them automatically :)

Are you maybe still in Classic? This functionality or similar is available in NWE but I don't think anything has been made available in Classic.