Given the functionality gaps between QlikView and Qlik Sense in general (and SaaS in particular), I'd suggest doing a redesign of your apps rather than trying any sort of direct / automated migration. Trying to bend Qlik Sense to behave like QlikView is an exercise in frustration for the most part, and the best choice is to avoid it entirely by rebuilding from the ground up insofar as the visual side of things.
Script-wise, you can largely re-use your existing scripts, after changing the connections/data sources of course.
I would strongly advise taking advantage of the Master Items functionality in Qlik Sense when rebuilding your apps, as this is something which was not available in QlikView and helps a lot with building consistent apps and with ease of maintenance.
A handful of specific things to watch out for:
* No cyclic groups in Qlik Sense (some workarounds exist and Qlik's latest Straight Table does have an Alternative for this, pun somewhat intended)
* Much weaker pivot table functionality than in QlikView, and well as weaker Straight Table functionality.
* No option to overlay objects (by default, at least, there are some workarounds)
* Generally, less monitor real estate to work with insofar as squeezing a lot of content into one page
* By default, Qlik Sense is responsive, meaning the sizing of objects and text might not behave as expected when working with different resolutions, zoom levels, and monitor sizes - something that needs to be tested and possibly adjusted for
