Does it possible to use formula field for calculating item's amount (lines) based on number at the header level? like a mixture formula based over data both from lines and header.

You may want to look into Main Line filter - header data with the same column name has Main Line = T

@Yadigar Have you tried creating a second custom field that is hidden and just sources the header value down to every line? Then you can use that value in your current field's formula. Alternatively, workflows or scripting.

@James Morris I have created one custom body field and another line field. I didn't manage to source the data from the body field to the line. I think that I must using scripting. If I could present formula at that line level based on transaction body field it via saved search it was great. Thanks again for your comment!