In Mockups 2, you could select the x/y position or size information for an object, and paste it into another very easily. This was possible because it used a single text field with a comma separating the x and y, hence you could select it all at once and paste it into your target object. I used this a lot when enforcing a common size across a bunch of objects that had already been created.
In v3 you have separated the x and y coordinates into separate fields. If there’s a benefit in this approach, I can’t think of it, but it’s going to cost me a fair bit of time.
I’d like to see the single, comma-separated field restored. Or even better, a direct option to clone size information from one object to another would be great, Whilst we’re at it, a “Format Painter” would be very useful too, for speedily harmonising colour, transparency etc across multiple objects