Just had a comment back from PCB fabricator Würth Elektronik: Please adjust the pitch between plated hole and micro via to min. 400μm". I have done this by creating a circle of 0.4mm radius on a drawing layer and then manually placing it over each via in turn, moving any microvias out of the circle. Any suggestions as to how I can either set a minimum distance for use during routing, or to automate the checking?
For pads one can set the clearance in the footprint editor… but so far I didn’t see anything like that for vias or micro-vias. 
There is also no setting in any of the files I checked for either the program or the project that would relate to via clearances.
Thanks. I think I need to place a feature request in the bug tracker.