Does anyone know how those flat plastic snap plugs come apart? The clear ones that connect appliances to ac power.
Thanks

Could you supply a picture of the plug that you're talking about?

Are you referring to the clear plastic connectors that are in line on the AC romex cables?

There are clips that you can carefully move out and then pull the connector apart, They really are not designed to be separated once they mate but I have done it. I have broken them as well. I usually see if there is enough wire and then take out that connector, it is a source of voltage drop and heat, found many quite brown, usually the ones on the coffee maker or microwave lines.

Yep! Those seem to have small "ears"on the sides that fit under tabs. I tried to disconnect the water heater for replacement but was afraid to break them. What do you recommend as proper plugs once I do break them?

If you have enough room and enough wire, you might consider a standard outlet box and duplex socket and use a standard plug from the water heater. I would use a 20 amp duplex and an industrial plug.

Have you ever used Wago Lever Nuts? They are being hyped for splicing and electrical distribution in homes.

Yes, but they usually require these to be in a box or other containment device. I have used them and liberally taped around them in an open space, not quite legal but never had a problem.