Files remain in queue after saving with external editor (Notepad++)

Using : WinSCP 5

Files remain in queue after I've saved them on an external editor.
I have to push the green > button to get them to upload saving when editing them.
Is there a setting somewhere to turn this off and on?

Please advise

You have probably turned off Enable queue processing for the session.
It's the first button on the queue toolbar.

Or you have even disabled it altogether by default in preferences:
https://winscp.net/eng/docs/ui_pref_background

Adjusting Background preferences as advised – returned background transfers to automatic.
I saved the session afterwards to make sure changes stuck.

Is this change to transfer preferences for this session – global for other existing sessions?

All settings in "Preferences" are global.

Thanks again for an excellent product.