added trips before/after switzerland tour

Are you thinking of Rick Steve's tours? There's several possibilities since Switzerland is a bit French, German and Italian so you could go in any of those three directions. We just went thru a similar exercise (with Tauck not RS) and the things we considered were:

-- Timing between the end of one tour and the start date of the next. If there was a gap how would we spend the time. Was there affordable lodging and things to do. I printed out blank calendar pages for 2021 to pencil in tour start/ end dates and looked at which ones were doable.
-- Transport between one tour and the next. How hard is it to get between the two tours. Train, plane, how many connections, $$, etc.
-- Weather and related wardrobe. Ruled out southern Italy and Iberian peninsula because I didn't want to have to pack for both cold and warm weather.
-- And of course is it an area you want to visit. We spent enough time in Germany last year so no interest is more.

We opted to join a tour in France with a gap of 3 nights to fill. Flying Zurich to Paris is pretty easy. Weather should be fairly close to the same since it will be Sep. Thought of the RS South of France or Eastern France tours but the dates just won't line up.

I have been wanting to visit Burgundy which would be easy to add to a Swiss intinerary.

Tours are tiring so allow several days before doing too much. You need to catch your breath!
Northern Italy and it’s lakes work very well with Switzerland. We have flown in to Milan MXP to do our Swiss trips that combine the beautiful Italian lakes, Maggiore and Como. We added Lake Orta once but did not like it at all. We rent a car in Italy, buy a Swiss vignette at the border , spend time in Switzerland and then drive back into Italy to Lake Como, back to MXP to fly home.
Another area that combines well is the Dolomites in N. Italy but you may have been in enough mountains.
Italy’s Piemonte wine country and seaside Liguria( Santa Margherita Ligure) are also easy drives from MXP.