Can I add records to a subform that has no visible field (on the form)

My Main form and subform are based on two different tables. I’ve setup the form so that the highlighted records from the Main Form are added to the subform when I click a button. All this is bog standard.

|Mainform| - - - - - - - - - - - - - |Subform|

Items —> (Save Record) —> Item list

However I don’t really want the user to interact with the subform. That happens elsewhere (I need to show the subform data with filters that interfere with the passing of records). But I can’t get the subform to accept new records without some active fields. I have “Update Form,” “New Record” and “Save Record” buttons, but unless I add a numerical field to edit some value on the subform table, the “New” and “Save” buttons are inactive.

I don’t have required fields, and relevant fields have default values.

I’m on the Base, using HSQLDB and Windows 10

It might help someone understand your problem better if you would post a ‘sample’ Base file (with dummy data)