Adding a top coat of hot liquid paraffin is in the "how to do it books" for storage of photo chemicals. I did this 50+ years ago in my home darkroom in the water heater closet. Better is adding clean marbles or using plastic storage bottles and squeezing the air out. I have used nitrogen filled bottles. I have used nitrogen filled storage tanks. I have used floating lids of paraffin. Common was polyethylene stars that floated on top in storage vats. The small star shaped hollow floats interlocked and thus reduce the air liquid junction. Many 4x5 and 8x10 hard rubber processing tanks came with hard rubber floating lids. Lots of ways to reduce evaporation and oxidation. Developer formulas all feature a preservative that retards aerial oxidation and reacts with oxidized developing agents to neutralize staining agents. Many of the other chemicals of the process also feature preservatives.

From the comments:

Please explain why the use of marbles/squeeze bottle to get the liquid up to the bottle spout (minimal oxidizing surface area) is better than a lid that brings the oxidizing surface area to 0. I could take a guess at it but I'd like to hear your perspective on it.

Protection against aerial oxidation can be a mix of things depending on the type of container and type of fluid. My mother used paraffin when canning fruit and vegetables. I used paraffin when I stored chemicals in canning jars. Marbles displace liquid bringing the fluid to the top of the bottle neck of glass storage bottles. Plastic bottles leach plasticizer depending on type of plastic and type of fluid. Bottom line, many ways to accomplish this task including switching to dry photography.