Enabling SSL would encrypt the connection between the source and destination. One of the main benefits of SSL is that MITM (man in the middle) attacks don't work on them as all of the data is encrypted in motion.
Now, if you are sending the credentials across in plain text, they are going to arrive in plain text. SSL protects data in motion, not data at rest.
An example of this, using SQL Server, is if you connect using a secure connection (ie SSL), and you type in "SELECT 'PASSWORD123' AS [Password]", the data is encrypted going from your machine to the SQL Server and encrypted going from the SQL Server to your machine, but at each "end" it is unencrypted. If someone has a tool for watching the queries executed against SQL Server (extended events and profiler for example) used by SQL Server on the server, they would see your query in plain text. If someone had access to see your computer screen, they could see the query results.
Now, doing a quick check on LDAP authentication via OpenLDAP (not a clue what LDAP tool you are using or how it is configured, it was just one I found) - it is possible to configure that tool to allow plain text passwords. The link I found states "OpenLDAP does support unencrypted, plaintext authentication, but the instructions for setting that up are non-existent" (link - https://www.digitalreplica.org/articles/openldap-for-ldap-plain-text-password-capture/). Now, Microsoft AD, from my understanding, stores the passwords in hashes. You can send the request with the HASH or you can send the request with the plain text password and AD can generate the hash to compare.
Based on your screenshot, since "use windows authentication" is unchecked, I would expect that you are either not using Active Directory OR you are not actually using LDAP for authentication. If you are using active directory, turning that on SHOULD (ie check the documentation for the connection as I am not an expert in all connectors) know it is windows authentication and allow for hashed passwords instead of plaintext passwords. If you are using LDAP, but not Active Directory, it may not hurt to try turning that on to see if your LDAP provider supports hashed passwords or not.
TL;DR version - If you are getting plain-text passwords sent across for the LDAP authentication, it is HIGHLY likely that you have either your LDAP provider configured to accept plain text passwords OR your connection manager is configured to send across plain text passwords.