We will plan to use Odoo V14.   

One of the new features of Odoo V14 is the ability to have Approval features in our Field Services App.  But right now, the approval feature can only work on Buttons. Since we don't plan to have our Approval process on the DONE button of the Task, we are thinking of creating a new button in the Form.   When we looked at Studio, it didn't allow us to create buttons in the Form.  We saw a video that told us to activate "Open developer tools", chose "Edit View: Form", and change the phyton code there and to add a new button.  

We understand the video and I think we can follow their instructions on how to do this.  

My question is, if we now play around with this code, does that mean that we can no longer keep on using the Odoo online platform and we will be forced to either move to Odoo.sh or maintain our system on premise already?  

Here is the link of the video I watched : https://www.youtube.com/watch?v=IlwLuu4EpIo

It tells me how to create buttons and use Server actions.