To open/show the form with with your own button or link you can use: srv.openModal(true,'formkey')
You can add this code to your button: <a onclick="srv.openModal(true,'form-key')">feedback</a>
You need to specify it with the form key, which is the unique identifier for that particular feedback form. You can grab that key from the preview page:
The full code for a link or button would then be:
<a onclick="srv.openModal(true,'2a8f783514fa91e03666bbb8c444ac4a0b967074')">Your feedback</a>
Then additionally, to hide the Mopinion button, go to the feedback form editor. (Replace "app" for your dedicated Mopinion subdomain if needed.)
https://app.mopinion.com/survey/manage -> Edit Form
And then click the Design Tab, and then the custom css icon in your theme.
There you add this line, but be sure to replace survey-key with the identifier of your particular feedback form:
And that's it... You are good to go!