All your code does is apply filter criteria and since there is no data in field to filter on, form is blank. It is not even coded to open to new record row.
If you want to create a record in tblCompanyDDIdentity that has CustomerDatabaseID as foreign key to link master and dependent records, either use a form/subform arrangement or code will have to pass CustomerDatabaseID value to form and populate field.
This is a common topic. Explore OpenArgs property of OpenForm command as one method of passing data between forms. https://www.access-programmers.co.uk...n-help.312716/
DoCmd.OpenForm "CompanyLetter", , , , acFormAdd, , Me!CustomerDatabaseID
Then code in form open event:
If Me.NewRecord Then Me!CustomerID = Me.OpenArgs