Currently mobile apps does not support Time Sheet for Jobs
it will be good to have a dedicated apps for Time Sheet entry.
Category: General
Ideas Administrator

Thank you for your valuable feedback. We have decided to deliver this idea and make it available with Business Central 2021 release wave 2.  

Learn more about what's new and planned for Unlock time sheets in Business Central using assisted setup and data entry on mobile devices here: https://docs.microsoft.com/en-us/dynamics365-release-plan/2021wave2/smb/dynamics365-business-central/unlock-time-sheets-business-central-using-assisted-setup-data-entry-mobile-devices  

Your help was greatly appreciated,  
Business Central Team