Add Custom Button below Create Fragment Option

I am looking for some resources, on how I can add a new button below the Content Fragment Option on /assets.html page. Once the user clicks on that button a popup should open asking for an id input, with that input I will call a servlet which will create the fragment in the backend and redirect the user to the edit screen for that content fragment.
The reason for this setup is, that we have multiple fragments, and based on the input id we want to decide which fragment model should be used, so this task we want to automate.
Appreciate any help regarding this.


