Hi BKlyn,
I assume that it might be possible.
Please take this documentation for a reference:
https://powerapps.microsoft.com/en-us/blog/build-offline-apps-with-new-powerapps-capabilities/
To create a SharePoint offline app, firstly, you may need to load the data on the startup of the app.
Please try to set the screen’s OnVisible property likes following:
If(Connection.Connected,ClearCollect(localtest,List1.Title);UpdateContext({statustext:"Online data"}),LoadData(localtest,"local",true);UpdateContext({statustext:"local data"}));LoadData(localtesttopost,"local",true);SaveData(localtest,"local")
Secondly, you may need to add a button to save the new item to the data source.
Please try to set the button’s OnSelect property likes following:
If(Connection.Connected,Patch(List1,Defaults(List1),{Title:TextInput1.Text}),Collect(localtesttopost,{localTitle:TextInput1.Text});SaveData(localtesttopost,"local"))
Last, according to the documentation, we may try to add a Timer control to auto save the data pending in a collection to the list. At here, you may consider to use the ForAll function.
https://powerapps.microsoft.com/en-us/tutorials/function-forall/
If(Connection.Connected,ForAll(localtesttopost,Patch(List1,Defaults(List1),{Title:localTitle}));Clear(localtesttopost),Collect(localtesttopost,{localTitle:TextInput1.Text});SaveData(localtesttopost,"localtest"))
Please have a try with it. Hope this could be your reference.
Best regards,
Mabel Mao