It is possible to import to Insert a CSV file including a list of visitor IDs. This list can then be used in audience filtering - you can build a segment including all visitors in this list or all visitors who are not in this list, and mix and match with other filters.
See this article if you are not familiar with visitor IDs and want to learn how to set the visitorID with the SDK.
Under the 'Account' tab, click on "User Lists". You can see the lists you've already uploaded to your account and can add a new User List.
The uploaded file should have a .csv type. The first line should include the string 'visitorId'. Then list the visitorIds, each one in its own line.
Note: It is also possible to create a list of Insert deviceIds instead of visitorIds. In this case the first line in the file should include the string 'deviceId'.
This can become handy if your app does not set the visitorId with Insert or if you want to refer to anonymous visitors. Another use case could be to build a list based on a survey's answer, you can find the device Ids in the survey export.
Once the upload is complete, you will see the new list in the table along with the number of devices in the list.
You can now create an audience for an insert via the new "User Lists" tab under Audience.