From the github features list… 👌🏻

Allow loading Glide typing library

not included in the app, as there is no compatible open source library

can be extracted from GApps packages (“swypelibs”), or downloaded here

if you are concerned about security implications of loading user-provides libraries, please use the nouserlib build variant, which removes this option. If HeliBoard is installed as system app, and swypelibs are available for the system, they will be used.