With the current vibration implementation through the Browser object, there is no way to set the duration / length of vibrations on ios (the value will be ignored).
I made this plugin which adds the cordova-plugin-taptic-engine by Eddy Verbruggen to the build service and comes with multiple actions that let the user add various types of vibration to their games. The actions represent the vibration types for the taptic engine introduced by Apple and explained here: developer.apple.com/design/human-interface-guidelines/patterns/playing-haptics
I have filed a feature request for this before, but unfortunately the devs do not seem to have the time to implement it (which is totally understandable, but I think this is quite important). Therefore, I figured I would try to implement this by myself and surprisingly it worked. I used the C3IDE for making this plugin and it is really amazing. Big thanks to piranha305.
Here is the link: construct.net/en/make-games/addons/923/taptic-engine-vibrations-c3