[IndispensableDestiny]

Years of physics and engineering study in the 70s and 80s; I never had to use the slug. Pounds-mass and pounds-force. You just had to know that one lbf equals 32.174 ft-lbm/s2. The “slug” is a derived unit to make one pound force equal to one of something.

[mrsmith]

Thanks, very encouraging.
Weird that this unit suddenly appeared.

[Dennis M.]

“Years of physics and engineering study..”

Same here. In my case CGS, MKS and Imperial were all required. In addition, E and M is split with two sets of units. You get used to it after a while but it is a pain.