There had been added the possibility to delete unsigned textboxes in timeline.
It can either be done directly in the textbox or it can be a global setting.

If done through the journal use the Delete button

It is important though that the textbox is empty before it can be deleted. Otherwise a pop up box will inform that the textbox needs to be empty.

A deleted journaltext can be restored by choosing the filter Show deleted

A button called Restore is visible in the journaltext.
By clicking on the lightbulb it is possible to get changes shown.

Choose the text that needs to be restored.

If a textbox is signed, the Delete button isn't visible.

Empty textboxes can also be deleted after a certain time through a global setting.
This only covers unsigned and empty textboxes.
Go to:

Frontpage - Settings - Choices - Values - Delete unsigned empty text after