Hi @guifluxe,
I am happy to know you are using the Inspections app. I created that app so hopefully I can help you with this. Would like to know a little bit more about the issue you are facing. Is your question about how to add one more option or how to display one more button for it in the app or both?
If you want to add one more option, you can go to the Inspections table, and then to the Outcome column. It is a Choice column and the Choice/option set name is "Inspection Outcome".

Then if you click on "Edit choice", you should see the 3 options. This is where you can add one more:

Once that is done, you just have to add one more button to the gallery, set its text to "Partial" and then set its OnSelect to similar to what you have on the other buttons. Let me know if you run into issues with this and I can help further.
Hope this helps.
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Thanks!
Hardit Bhatia
Microsoft Business Applications MVP
Microsoft Certified Trainer MCT
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