Recently the app got the ability to display custom flags, but you still can't select it. The 4chan API accepts a 2 letter code in the form field "flag" that gets sent to post on /pol/. The 4chan board API has a board attribute "troll_flags" that will be set to 1 on boards that have them (currently only /pol/) and a list of flags and their codes at the end also under the name "troll_flags", so these could probably be put into a spinner or something.
Recently the app got the ability to display custom flags, but you still can't select it. The 4chan API accepts a 2 letter code in the form field "flag" that gets sent to post on /pol/. The 4chan board API has a board attribute "troll_flags" that will be set to 1 on boards that have them (currently only /pol/) and a list of flags and their codes at the end also under the name "troll_flags", so these could probably be put into a spinner or something.