On the Create AAVSO Report form there is a field for 'group identifier' under the field for observer code. What should be entered for the group identifier?
The group identifier is optional, it is just a way to label related observations. If you have a set of BVRI images of a target, you can label them with an identifier. From the AAVSO documentation:
Grouping identifier (maximum 5 characters). It is used for grouping multiple observations together, usually an observation set that was taken through multiple filters. It makes it easier to retrieve all magnitudes from a given set in the database, say, if someone wanted to form color indices such as (B-V) with them. For cases where you want to group observations, GROUP should be an integer, identical for all observations in a group, and unique for a given observer for a given star on a given Julian Date.