Is your feature request related to a problem? Please describe it.
There's no way to add conceal for unicode-math standard commands \symbb etc. even by #1972 custom conceal methods.

Describe the solution you'd like
For the simplicity of implementation, I would like the corresponding commands (e.g. \symbb to \mathbb, \symit to \mathit) to be concealed alike. Maybe in a individual syntax package for unicode-math.

Describe alternatives you've considered
A more general way is to allow users to add this correspondence manually, as is mentioned in the previous issue.

Additional Info
The unicode-math package commands: