Add Custom Fields to store admin part (Taxes)

Hi,

I’m a developer, but I’m new to WP and Marketpress.

I’m working with a multisite installation. It has MarketPress and Custom Press installed.

I need to add custom fields for store admin section (for all stores that exist and future ones). It’s for Taxes Purpose. I posted the question in one of the other posts, but I don’t think anybody saw it: (https://premium.wpmudev.org/forums/topic/marketpress-calculate-sales-tax#post-438129)

My questions so far are:

– is there any existing solution for this?

– Can I use CustomPress for adding custom fields into store-admin site section?

– Can u list documentation resources that I should start with if I need to do it on my own?

– do I need to create a separate plugin to include this feature or I can modify the marketpress files / frontend editor files for that?

– what is the right way to install new fields into the db for multisite marketpress site? (documentation on this part)

Thank you,

Lex

Could you please point to me resources that might be helpful.