Notes Field, Is that still Available?

As a custom field, yes. Your software is quite far out of date. Not only can you still have a Notes field, you can set default content under Form Defaults. Update your software, and read these Guides:
https://www.manager.io/guides/8941
https://www.manager.io/guides/14059

If you had content in any Notes field for a particular form type, updating your software will automatically create a custom field for you and transfer existing content. Nothing will be lost.

I am using Latest Software, I just shared the image of old software. Actually i wanted footer in Invoices which i am unable to do, After pressing Edit in Template i am still not able to configure Footer for Invoices . because no html template appears .

Thank You TUT for previous reply, I am back to manager after 4 years!
This is exactly what i want, Buy it does not appear at all

Untitled|690x340

@Tut please do check the detailed comment above

If your version still has sales invoice template as a feature, it is years out of date. And nowhere should you expect to see an HTML template. Themes replaced the sales invoice template feature long ago, and broadened it to cover all transaction types. Themes are written in Liquid.

If you were using the term Template when you actually meant Theme, then you must first create a custom theme. Only then can you edit it. See https://www.manager.io/guides/10368.

I think easier is to just add custom field called Notes to sales invoice. Themes would be more suitable if you want to change the layout.

Guide for custom fields is here: https://www.manager.io/guides/8941