You could do what I did -- you are part way there already. You would need to build and use a custom kernel, as fuse kernel services are not part of your 5.4 GENERIC or GENERIC.MP kernel. Fuse kernel services were enabled for -current users 1 November.
That stated,
I wouldn't recommend doing this. While you could certainly configure and build a 5.4-release kernel with fuse included -- custom kernels are unsupported, and you would be using code that was (at the time) experimental and incomplete.
In order to run -current, you must either re-install from a snapshot, or do a
very careful upgrade with a snapshot.
Very careful. Due to several changes to application binary interfaces between 5.4 and -current, a -current kernel is incompatible with 5.4 userland and port/package binaries.
That ABI incompatibility precludes you from running a "Frankensystem" with a blend of -release and -current components, if you were inclined to experiment.