@brian-eastham-0 You can do this with just a little more effort than ‘pressing a button’. You need an adapter - something like one of these:
(If I recall correctly, Apple provide such a thing at a typically extortionate price, but the one above is a very low cost item from eBay, it works perfectly, is versatile and it lives in my tank bag precisely for this purpose. Similar things are available for Android devices I would imagine, though some might even have slots for SD cards?)
…and a formatted SD card suitable for the model of BMW Navigator you own (some Garmin devices can only use relatively low capacity cards, such as 8GB and below, so worth checking).
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Create your route on your phone (using MRA Routeplanner, of course!)
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Plug the adapter (with SD card inserted) into your phone - it will automatically be recognised and listed as a location in your phone’s ‘Files’ app (e.g. the location in my phone’s app is ‘NO NAME’ with the card I just used to run through the process, other cards might yield ‘8GB DISK’, etc…)
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In Routeplanner, save the route (as the appropriate file type for your sat nav and your preferences)
to a suitable location in your ‘Files’ app (e.g. I created a folder named ‘GPX Files’)
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In ‘Files’, copy the new route to the SD card’s location (Routeplanner doesn’t seem to recognise the SD card directly, hence this step)
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Remove the SD card from the adapter, install it in your sat nav and import the route from card to your device's routes folder. (I don’t know how that is handled on BMW versions, but on my Garmin Zūmo 390, for example, it’s all within an app called ‘Trip Planner - I open that and the import function is within it. I doubt it’s too different on BMW devices?)
This process can be followed while on the road and, though it might seem a bit of a faff from reading the above, once the route has been created it actually takes seconds to get it from phone to sat nav in practice. Obviously, it can be used in much the same way to transfer existing routes too.
I hope this is useful?
I just hope my workaround is of use to 
My VFR800 has five hard wired on the bike and my tank bag has another four!