How i can create veriable items

I have clothes business. I have one Dress style in different sizes and colors. How i can add items with size and colors and can purchase items with size and sale with size and color.
Actually i want to keep inventory stock by size, color and brand.

Each item (size, colour and brand) will have to be a separate inventory item

Mean 1 style of dress i have 9 sizes and 3 colors. then i will create 27 items code.

Yes

How else would you keep track of them?

Before i was using one software there was option that one item i can select color and size then infront of each size i can enter qty. and when i am selling same selecting size and color.

Please advise me how i can add custom field in item rows in invoice. because if i have custom field of size and colors in invoice then i cannot enter different items in one invoice

Read this Guide: https://www.manager.io/guides/10411.

But you do not want to do things that way. Those fields will only be for information on the invoice. Dresses of different sizes or colors will not be tracked separately. Manager assumes all units of an inventory item are identical and has no subsidiary categories. So if you want to know how many red dresses and how many blue, you need two inventory items. If you want to know all your sizes and colors, you need all 27 items.

Thanks Tut.