Subway Tooter@BioFris ST provides client-side keyword muting for historical reasons, but after Mastodon's server-side keyword filtering implementation, it appears to users that the same functionality exists multiple times with different names. There isn't much prospect of extending client-side keyword muting. Your suggestion should be made to the Mastodon official, not the app
GNU social JP is a social network, courtesy of GNU social JP管理人. It runs on GNU social, version 2.0.2-dev, available under the GNU Affero General Public License.
All GNU social JP content and data are available under the Creative Commons Attribution 3.0 license.