Save List

You can save the filtered leads as a list for your future reference

Step 1: Go to Lead List

Step 2 : Apply required filters

Refer Filtering Leads article here

Step 3: Click the arrow next to Apply Filter, then select Save List, The following

Step 4: Add Visible to Users and If you wish to refer leads, add users in Assigned To

Step 5 : Click on Save List

You can merge new leads with the existing list as well. Just Select Merge with Existing List option.