A best practice is to maintain the "All Leads" list with only active leads. This means that if a lead's deal(s) have been qualified as won, lost, or abandoned, and there are currently no other potential deals to pursue with that lead, it is advisable to remove the lead from the list and mark it as inactive.
1. Select the lead to be removed
2. Click on "Remove Lead"
3. Confirm action
Inactive leads can now be found in here
To re-activate a lead you can follow the same steps as when creating a lead