You can dismiss tiles (Sync, Shelf, Library...) by adding trigger to sqlite file.
1) Download sqlite editor, I'm using
SqliteStudio.
2) Backup the sqlite file from your device, X:\.kobo\KoboReader.sqlite, just in case, copy the file to folder in your PC.
3) Open SqliteStudio, database > add database ,X:\.kobo\KoboReader.sqlite.
4) Select Table:Activity and go to Data.
5) You can see all the tiles on the device, the tile Type and Enable (true or false).
go to Triggers > Create Trigger.
6) Now write a trigger to disable a tile, example Sync.
Name: Sync
Action: UPDATE
Code:
UPDATE Activity SET Enabled='false' WHERE Type='Sync';
The tiles dismiss only after reboot the device, exiting nickle or connecting the the device to PC.