theres many ways to accomplish this.
you could check to see if character overlapping trigger box before running the actual jump script. so it would be something like input event → get overlapping actors of type trigger box, get length, length > 0 → branch, if true jump.
or theres always the on begin overlap, cast to triggerbox, is success set canjump? variable to true. then have the jump input, is can jump true branch, if yes jump.