You will most likely be happier using your existing lens for 35mm, and the longer lens for 6x6 and 6x7.

Enlarging lenses are optimised for a range of magnifications. An 8x enlargement is at the top of the range for most 80mm lenses, whereas a 50mm lens is most likely to be designed for an 11x14 print.

In addition, the 50mm lens will permit using the enlarger at a more convenient height (thus limiting the danger of vibration).

Both approaches will work, but I think you will be happier using the 50mm lens you have for larger prints from 35mm.

For smaller prints, you may be happy leaving the 80mm lens installed.

Which version of Schneider lens is it?