If there is a SavingMechanism available that supports it, TiddlyWiki will automatically trigger a save of the current document on clicking ok or delete when editing a tiddler.

You should see a yellow notification at the top right of the window to confirm that an automatic save has taken place.

Automatic saving can be enabled or disabled through the Settings tab of the control panel . Behind the scenes, it is controlled through the configuration tiddler $:/config/AutoSave, which must have the value yes to enable automatic saving.