Will there be support for Splash player by Mirillis?

I tried to install K-Lite codec pack for Splash player but it doesn't show up in the File Associations part of the installation. Will there be support added for this player?

No, there won't be file association options for that player. Players typically already have their own options for file associations.

Any player that is capable of using DirectShow filters, can use the codecs from K-Lite. I don't know if Splash uses DirectShow. It might only use it own internal codecs.