To create a custom influencer list, please click on "Create a new custom list of creators" in the "Target audience" section.
From here, you can either manually enter the names of all the creators you want to add to this customized group, or directly add a list of influencers by importing a list.
 
Keep in mind that the criteria's selected via the previous filters may not apply to the influencers added within your custom list!
These two groups will largely be  independent. However, this still allows you to add influencers from the filters selected in addition to the ones from your custom lists.