Welcome to the community!
The Tasker integration with the openHAB Android app only enables us to send commands to items from Tasker. To go in the other direction, I send notifications to the openHAB Android app and have Tasker act on them.
- Create a rule that triggers on item changes, with the sendNotification as an action.
- Create a profile in Tasker that monitors the openHAB app and triggers a task to update your variable (or do whatever).
I also use the Notification Listener add-on to delete notifications. Tasker doesn’t have that capability built in.