Q. *vistë n. “change”
This word is unattested, but there is indirect evidence for it as an element of walwistë “change of mind” (PE17/189). This word likely contains the archaic form †wistë from before the change of ✶w- to v-; the ancient w is preserved medially after the n. Its later form would be vistë. If you accept inwist- as the stem form of inwis “change of mind”, it likely contains †wistë as well.
There is another attested word wirne with the gloss “change” (PE17/191), but I think it is likelier to be the archaic form of the strong-past tense of the verb virya- instead of a noun.
Reference ✧ PE17/189 ✧ #wiste “change”
|√WIS > #wiste||[wiste] > [βiste] > [viste]||✧ PE17/189|