Adding pretty permalinks to my plugin

I am writing a plugin that by default is accessed by

https://example.com/pluginpage?parameter=value

I would like the links to look like

https://example.com/pluginpage/parameter/value/

I would prefer to do this with .htaccess, but tapping into the inner rewrite engein in WP is also viable.

My current .htaccess looks like this

Options FollowSymLinks
RewriteEngine On

RewriteRule ^pluginpage/([^/]+)/([^/]+)/?$ pluginpage?$1=$2 [NC]

# BEGIN WordPress
...

But this renders me a 404 when trying.

Anyone who could give me a pointer?