Hi,

This is probably not what you want to hear but 2.46 is now 11 years old, released in 2005 while the 16F1786 seems to have hit the market around 7 years later.
Support for it was added to PBP in version 3.0.7 back in 2013.

I don't know if it's possible to "manually" add support for that chip in the 2.46 but what you can obviously do is to upgrade you version to something a "slightly" newer.

/Henrik.