The location of the repository database would depend on how your system was set up by the administrators and would be available in the admin console.

However, what you're describing wouldn't necessarily be a straightforward query and directly referencing the db is not generally recommended so extreme caution is required.

Laserfiche doesn't exactly store the "path" of an entry in the database, rather it tracks the Parent identifier which in turn references another entry in the database.

As a result, if you have to include subfolders things get a heck of a lot more complicated.

A better option might be to approach things the other way around.

You can configure custom tabs in the Web Client and those custom tabs allow you to use variables in the URL, and you can populate most variables in a form via URL.

For example, you could create a custom tab that links to https://yourserver/forms/yourform?Id={id}

Where "Id" is the variable on your form and {id} will be dynamically populated with id of the selected entry.

That way they can just select the document to which they want to append, fill out the form in the custom tab, and do it all without having to enter a title or anything.