How to identify whether the edit mode is active

The edit mode is displayed in the header. If it is not active, only the symbol and Edit are displayed:

Edit mode off

Clicking Edit > Edit Contribute enables the edit mode.

If the edit mode is active, this is shown in the header:

Edit mode on

Clicking Editing off Exit edit mode disables the edit mode.

The availability of various edit boxes is another clear indication that the edit mode is active.