I agree with @Robert_Petitto. You shouldn’t be setting a filter, because if you use a relation as the source of your list, it is already filtered with the correct data.
To explain your problem with the same changes being made on every category…those categories are all part of the same sheet and screen layouts are tied to sheets. Your filter setting is part of the layout for that detail screen, so it’s going to be the same for each category. Like @Pablo_Reyna mentioned, you can turn on independent screen configuration to independently configure each screen, but it becomes a problem if your category list keeps changing or if you want similar layouts for each category, but you then have to design each one separately, which can become tedious.
I think the proper solution here is a relation in your category sheet that links the category column to the category column in the sheet that contains the related items.