Can a 68C (Licensed Practical Nurse) fill a 68W (combat medic) slot within a unit?

You can fill the slot on a unit's UMR, but you would need to meet the certification requirements of a 68W in order to be deployed and/or clinically function in that position. Typically, the 68C, in the hospital setting, is higher on the food chain then the 68W, but, in the field setting, the 68W has more focused training.
The 68C is generally not as well trained as the old 68WM6 was...The M6 ASI was an added identifier for an LPN with 68W capabilities

I know a while ago the Army moved to allow Charlie's serve in Line units. But, I thought they stopped that practice. It may be that this particular practice is still in play. That's the only thing I can think of.

Pretty sure that's a yes but more importantly
you could fill the PA (Physicians Assistant) Slot.

No, they cannot

Yes you are a medic the only difference is push medications. Thank you for your service

Back when I was a 91B20, 91Cs were assigned to Medic Platoons as Squadron/Battalion Aid Station-Dispensary staff along with the PA and MD.

Obviously things have changed since I retired, but when I started 68W was a prerequisite for going to 68C. I enlisted as a 68C, but had to go through the then 68A school first. If that was still the case, then I would say that a 68C would be able to fill a 68W slot.

Okay, I know I am going to officially sound like an old timer but in the 1980s all 91C, the previous designation of 68C were first qualified as 91B, combat medic, currently 68W. Almost all medical MOS'S had to do 91B school. Army doctrine was that all medical personnel were 91B, or combat medics, I was a surgical technician, 91D, the current 68D, but I had to do Medic school first. Medic School (91B) was not as long or as thorough as it is now. Physicians were all as a primary role, Battalion Aid Surgeons so even psychiatrists and pathologist, pediatricians all had to do a weekend in Emergency room doing trauma every month.

Why not wander into the BDE S-1 shop and ask the S-1 NCOIC why you're being transferred to a slot you can't hold by MOS... hummmmmmmmm...
I wonder just how many 68 series MOS's are homesteading MEDAC/MEDCOM units and not gaining the "LOVE" of Combat Arms, Combat Support and Combat Service support units...

"Hello, my name is SFC____________ I have spent the last 12 years of my Army career at _____________ Medical Center, I'm your new Platoon Sgt"... "Welcome to_________ Inf. AR, FA", "I'm SSG___________, I'm your current EVAC Section NCO 'Lord help us'" Worse than greenhorns

I'm in a medical unit. Haven't heard that before. We have Medical officers who are RN's and some enlisted who are also RN's. The enlisted still operate as 68W's but that's because our unit does not have 68C spots and they all trained and joined the unit as 68W (Certified EMTs). Our brigade nurses are all officers and hold positions in that capacity.