Hi mike. dash ,
We do not allow a user to delete specific data from a dataset unless they are deleting the entire dataset or a daily file from that dataset. If you are wanting to remove a subset of tags, you can mark it for obsoletion using the admin or remove it from the data collection source. It really depends on the Canary Collector you are using.
If using the Logger Admin (OPC DA) or the OPC Collector (OPC UA), there is a checkbox to create a new file when logging begins which forces the historian to create a new file only containing the tags from that logging session. This does not actually delete historical data for those tags, but removes it from view so it is no longer available for clients coming in to browse and consume that data.
If not using one of the two methods of data collection above, there is another process for obsoleting unwanted tags from a dataset. That methodology can be found here, Obsoleting Tags from a Dataset.
Metadata can be removed at a dataset level across all tags by clicking on the white down-arrow...
...or on a tag by tag basis when you choose a specific tag then select the yellow down-arrow.