Inserting Tuplets/Ratios over barlines and across more than a beat

How do you insert tuplets over barlines (ie play a sextuplet starting on the 'a' of four and finishing on the 'a' of 1 of the next bar)? I circumvented this issue earlier by just changing the time signature to 5/4 then 3/4 then back to 4/4 so that it didn't cross the barline but I still had the same number of total beats. I was wondering if this was possible.

My second issue arose when I wanted to add a tuplet ratio greater than a beat. I was attempting to add a 6:5 polyrhythm in 4/4 (so think six notes played in the space of 5 sixteenth notes) and I could not figure out how to do this. There's no way for me to notate the value of 1+1/4 and simply highlighting a quarter note rest plus a sixteenth note rest doesn't work either. I was wondering if this was possible. Thanks for any help!