You are actually can enable or disable the plugin steps through CRM Web UI
This is the step if you use the CRM UI to disable the plugin step:
1. Go to Settings --> Customization --> Customize the System
2. In the left navigation you can see 'Plug-in Assemblies' and 'SDK Message Processing Steps'
3. Go to SDK Message Processing Steps
4. Then, you can select the plugin step you want to disable
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You can select more than 1 (multiple select) as well
5. Just click the Deactivate ribbon and next to process
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6. You can see the status of those steps now
7. Here is the status:
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Hope it helps!
Thanks
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