Is there any way to fill empty space in a uv area considering another part of the uv that i want to keep immobile?

I have made some content for my The Sims 4 and there is a big limitation regarding the free uv area, since The Sims 4 is one of those games that put all the avatar content in one image … (image of the uv area attached below)

I would like to know if there is any way for me to automatically fit the uv of my clothes in a specific area, without overlapping the uv I want to keep immobile, just using free / empty areas … any plug-ins or something?

in advance, thank you very much !!