The Last-Modified field of web-app changes once a web-app is saved after any modification. The Modified By field also changes with the mapping of the Operator who changed the web-app.
If I were to track this, I would create a new schema with fields > Modification Date Time, Modified By, and Web-App ID
This schema will be 1-N mapped from the web-app schema and 1-N mapped from the operator table.
Now I would create a new workflow with a scheduler, query, and update data activity. The query runs on the web-app schema and pulls all the web-apps with a primary key greater than 0. Pass the web-app ID, modified by and the last modified fields downstream the workflow. In the update data, use reconciliation on web-app ID and last modification date time with the new schema that you created. The idea is, if the last modified date time and web-app id do not reconcile with any entry of the new schema, that means it's either a new web-app or an old web-app that has been modified. In case of no reconciliation, this will create a new entry in the new schema with the web-app ID, last modified date time, and the modified by data that comes from the query.
Since the web-app table is not a big table, you can schedule this workflow to run every 5 minutes to track changes in the web-app table.
Note: The workflow needs to execute at least once before the above logic becomes helpful. Basically to fill the new schema with the current web-app table data. In the next execution, it can track changes.