On the app store version zap is only on the profile card, the direct download from https://nostur.com has it on posts.

You can also close the app and type on the Terminal:

defaults write nostur.com.Nostur footer_buttons "\\Ud83d\\Udcac\\Ud83d\\Udd04+\\U26a1\\Ufe0f\\Ud83d\\Udd16”