One way to accomplish this is with free format questions. I created a free format question "FreeFormatQ," added a hidden variable "FreeFormatQ_Var," and then used this HTML:
<button id="toindex">Skip to Index</button>
<input name="FreeFormatQ_Var" id="FreeFormatQ_Var" type="hidden" value="0">
All that's left to do is to create a skip that triggers when FreeFormatQ_Var = 1.
Heads up: As this involves submitting the page, the skip will only occur if the respondent has answered all questions on the page that require a response.