Current version of Qlik Sense doesn't this feature.
Check this below link ( officially it's not yet released in IOS app Store, hopefully by this month end)
Note: Qlikview has this feature (mobile offline - ios device)
Hello seen in support site : https://qliksupport.force.com/articles/Basic/Qlik-Sense-Desktop-Support-FAQ
Can I use Qlik Sense Desktop if I am not connected to internet?
When you open Qlik Sense Desktop the first time, you will need to log in with your Qlik Account to be able to use the product. You will be able to use the product offline for 10 days from the last time you logged in.After 10 days have passed, you must get connected to internet and log in again to be able to continue using the product offline
So, if you've get connected (internet validation) in the last 10 days, offline use is possible and will not show you login screen (connects directly) - tested with Qlik Sense Desktop September 2018