How to Address Forehead Numbness After a Browlift?

The type of browlift you descirbed usually spares the nerves exiting from the skull and innervation the brow and scalp.  Short term anesthesia is common but after 11 months, I would be a bit pessimistic.  Sensory nerves, however, might repopulate the area in the future so don't give up.

This may be permanent. There is no way to determine this for sure.
Surgical exploration could perhaps determine if the nerves were severed. In this event repair could be attempted but would not likely to be successful.
Essentially you are describing two different issues.

One is pain
The other is numbness.

To some degree they are related and treatment depends on your goals.
To manage the pain, you may want to massage the area, or use topical creams with capsacin (pepper derivative) which distract the pain fibers similar to a TENS unit for the back. Alternatively, if there is one highly sensitive point, it may be indicative of a neruoma which requires removal and will defcfinitely leave you with permanent numbness.
To treat the numbness, the options are surgical repair (with low likelihood of success) and at great expense or tincture of time. This could see some improvement over two years.