Sure, you can simply move one or more leads across your lists in the Leads section of your account in a few clicks.
While on the original list's page, select the leads you would like to move;
💡Note: You can select all leads from a list at once by clicking on the checkbox in the header next to the ''Email'' column;
Click on the Actions button and then on the ''Move to a list'' button;
A popup page will appear. Select the destination list and confirm the change by clicking on ''Move leads''.
💡 Note: To move a lead, you need to be inside a specific list, rather than on the "All leads" page.
How to merge leads
You can also move an entire list of leads and merge it with another list by using the "Merge with another list" option:
Click on the arrow next to your list's name;
Click on ''Merge with another list'';
A popup page will show up to select the ''Destination list''. After selecting it, click on ''Merge lists''.
For more details, you can read the section about lead verifications in the main Leads help article.