Yes, you can edit/duplicate/void a journal.
The options can be found in the 3 dot menu.
Juan allows editing for the following journal types:
Manual Journals
Cash Journals
The following journal type cannot be edited:
Transfer Journals
Juan allows duplication for the following journal types:
Manual Journals
Cash Journals
Transfer Journals
If the journal was manual, adding a payment account will classify it as a Cash Journal.
If it was a cash journal, removing a payment account will classify it as a Manual Journal.
You can duplicate a voided Transfer journal.
You cannot duplicate a voided Cash and Manual journal.