Oh, finally remembered that I can put resize set width command into a for_window clause to get some of my GTK apps resized to a small sidebar on my display. Bowl looks much nicer on a small display; mainly because only the post composer widget is implemented, and a two-column layout that I'm thinking of will require a few more things the app lacks for now.)

Now, if only Sway included a positioning command that puts windows relative to the top-right or bottom-right corner...

(I suppose that is not hard to implement; I was able to implement it using an external script, but an external script incurs a delay that native commands do not. Thus it would be beneficial to patch Sway to support corner-relative window moves.)