If I understand your question correctly, you would like the user of your app to change the text that appears on your app so that is can be written in their own language or for it to say whatever it is they want it to say. You idea was to create a long list of
inputs to accomplish this.
As for if that's "bad"... there is no good or bad in UX, just a degree of usability. Any long list is "bad" in simple terms because it's harder to use than a short one, but there might be good reason for it. If there isn't though, you should always keep things simple.
I'm assuming all this text is not on one single page in the app itself. My recommendation would be to allow each page to enter an "edit" mode, where the text that is able to be changed is replaced with a
input element that the user can interact with. Once they make their changes, they can exit the edit mode and these changes are saved.
This will avoid your giant list problem, as the text will be broken down by each page.
From your screenshot, I can already tell you the list will be too long. Especially for mobile. It will be too easy for the user to get lost. Consider only using one input for each text item and just have to user write over it. That will essentially cut the length of your page in half. Additionally, breaking it up into categories as you mentioned would help a great deal, as long as the categories make sense. On top of that, you can have the user search for a particular input, meaning the list would be filterable.