Hello,
copying fields is still possible, with the keyboard:
- Click the field so that it is selected.
- Press Ctrl+C.
- Press Ctrl+V. The copy is inserted a little offset from the original and gets a name of its own. Each further Ctrl+V inserts another copy.
While the cursor is in one of the input boxes of the field properties, Ctrl+V pastes text there instead of a field.
At the time of your post, copying had some bugs: copies could lie on top of each other or disappear when saving. This is fixed in the online tool https://tools.pdf24.org/en/make-pdf-fillable. In the PDF24 Creator (Toolbox, Create fillable PDF form), the fix will come with the next version.
If you open the tool via an old bookmark: the address create-fillable-pdf-form now opens our new tool for designing a form from scratch. To add fields to an existing PDF, please use Make PDF fillable (link above).