What's the use of the tax1, tax2 and tax3 columns

[joebordes]

I'm not sure I am following you. The application has three tax types configured by default, thus you have three columns, one for each type. If you add another one you will get another column in that table.

See the attached images

Maybe you have them deactivated?

Also, you have to establish the different tax amounts per product in individual mode.