To be able to add leads to lists when the limit has been reached, follow the steps from your main dashboard:
Go to Data Management
List Management
Add list
Use the search box to find the list
Select
Add Contacts/Leads
Scroll down the page
Tags -> add the tag used when uploading the file
Or use Batches -> add the batch name from your imported file
Preview
After Clicking 'Preview', you will be able to identify if there are more than 100k leads, if that's the case, you need to click the "Confirm and Add" button and "Create" a new list again by following the same process.
When creating the second list to add the remaining leads, use the same name as the initial imported file but add a "2" to differentiate it from the first created list.