What if i am willing to position my custom fields in mid of the for loop. like code category, size, description and so on.
What does this have to do with customizing invoice numbers?
change labels and to add few column like Category sub Category and as needed in many other forms.
Your question was moved to a new topic, because none of what you ask about is related to invoice numbers.
These Guides may be helpful:
https://www.manager.io/guides/10411
https://www.manager.io/guides/17100
If you do not personally have the software coding skills to do what you want, you will need to hire a local programmer to write a custom theme for you.
Thank you.
I saw those before. Okay i will find my way. Have to learn these new things with liquid to get in.
Just now I need to change few labels like due date to delivery date, invoice date to date etc.
themes are not editable now 
The default themes have never been editable. You need to use COPY TO NEW THEME of the default existing theme and these you can rename and edit. Terminology for Manager version 21.6.33
using replace code u can get the desired results with some hit and try method.
Thanks for reply.
Well, trying to make some change on my invoice.
{{ column.align }} column.nowrap how to set these two attribute/property in manager.