Get Field Values from previous form

How can I carry a value from a form into a second form when the first form has not been saved yet? If this makes sense and you have an idea, you need read no further….

I need to get a value from an initial (unsaved) form into a second form.

It may help to describe the process:
I have physical cabinets which contain switches. The switches within the cabinets are inspected on a cycle.

The app database (google sheet) contains 3 tables: Cabinets, Switches, & Defects. (There are others such as schedule which may not be relevant at the moment)

Switches are related to Cabinets. Defects are also directly related to the cabinets. A cabinet is inspected and if no defective switches are found, a new row is entered into the Defects table reporting ‘No Defects’. If a defective switch is found, a row is entered to record the defective switch.

In the form (1st form) to create the defect is a drop down field to pick from a list of switches which are related to the cabinet. This works if the table of switches contains switches which are related to the cabinet. My problem is when there are no switches related to the cabinet. From within this drop down field, the user has a option to create a new switch. Clicking the ‘new’ option opens a new form (2nd form) to create a new switch. The problem is that I cannot populate the related CabinetID field.

How can I carry a value from the first form into the second form when the first form has not been saved yet?

@Steve