wp_kses_post: add custom protocol to whitelist

Hi,

I’m using the wp-tiles plugin to show a few custom posts as tiles.
The plugin allows to define content that’s shown on top of a tile via a template.
Inside the template you can access post meta via a “%meta:MY_POST_META%” string.
This works perfectly fine but if you load more tiles via ajax (the plugin supports this) the template string is passed through wp_kses_post and the “%meta:” is stripped inside a href value (i’m creating a list of links on top of the tile).
I’m guessing this is stripped because it’s interpreted as a bad protocol.

Is there any way to add a custom protocol to the kses whitelist or another workaround where i don’t have to edit code outside of my child theme?

Any form of input is appreciated 🙂