I did this on one of my customers instance and this will solve the problem to hide the button for specific table:
1. In the application menu go to declarative actions > form actions
2. Search for Action label "Open create collab chat modal" -> Choose the one applying for your app (Task table if your table is a child of it)
3. On the record you will see a related list "Action Exclusions"
4. Open that related list in a new window to have it filtered for the Action (Table name "sys_workspace_declarative_action_exclusion")
5. Create a new record with following details:
- Action assignment: keep as is
- Table: Insert the table where you want to hide it
- Exclude this table: true
- Exclude all child tables: true if you want child tables under your app table also to hide it
- View: If needed add a specific view to hide it
6. Submit the record and you should see it under the related list "Action Exclusions" in the Declarative Action
Action should be hidden now on your form.
Alternatively you can create a record in table [sys_cs_collab_enabled_table] for your table and set active=false. It should also hide the button
