I have some linked maps, where I want to filter by due date, across the linked maps. I want the results to be shown on the one screen. Is that possible?
Yes you can, provided you have a later version of MM2017, or MM2018 or - in theory - MM2019 (more on that later).
You can create a dashboard map which rolls up all the maps you need, linked or otherwise. When you do so it's usually easiest to select the central topic of each of the maps - unless all the tasks are contained in one or two specific branches, in which case you could select just the parent topic(s) for those branches. Then in the dashboard map, click on the Map Roll-up icon for the linked topic and select Show Topic and Branch.
When you have finished adding all the maps you want to include, save the dashboard map and apply a filter for the dates you want - only the relevant tasks (and their parent topics) should appear. Don't forget that if you change the due dates of any tasks in any of the rolled-up maps you will need to close and reapply the filter. This also applies if you add new tasks to these maps, and you should also do this whenever you reopen the dashboard map.
In relation to MM2019 I'm experiencing a bug which causes MindManager to freeze whenever I try to apply a filter based on task due date, whether it's a dashboard or ordinary map. I'll report this separately to Mindjet/Corel; hopefully it is an isolated problem.