I'm using an ageing Nexus 6 with stock and rooted Android 7.1.1. The problem I have with most multi-featured keyboards is that they don't hide timely with my pace of app usage. So, with animations disabled, when I swiftly switch to an app and the keyboard was opened in last used app, it would not hide out with a breeze. Often I find a gap of one or more seconds which is irritating and unproductive.
Using Back key doesn't really work in such cases. I tried Hackers Keyboard while looking for a lightweight keyboard and while it provides a swipe action to hide keyboard (which reduces the severity of the issue here) I have productivity issues with the low and rigid width of its space bar which I have discussed here. Furthermore, it lacks predictions which is another disappointment.
Ideally, I would prefer to use my Gboard or any alternative but competitive app but the competitive ones I tried, such as TouchPal, Swiftkey, Google Indic, suffers from performance issues on my device. As such, I'm looking for a way to hide any keyboard with a gesture and swiftly.
I tried to look for Xposed modules but to no avail. I also looked into GMD Gesture Control to my utter disappointment.