I do that all the time: - Install maps from Velomap.org to Basecamp - Copy using Garmin Mapinstall to the watch, while removing maps not needed for the moment.
Sort of a topic drift, but how does one replace the default route maps that comes with the Fenix 5X? Mine was a gift that was apparently sourced from the UK, because while it has highly detailed European maps installed, the North American maps appear to be simple base maps, not detailed route maps.
Don't delete them , move them somewhere safe and just copy them back when needed
And do not forget to move (backup!) also files with extensions: GMA, SUM & UNL !!!
In fact, it would be wise for each owner to backup whole directory structure with all the files (even hidden ones!) and especially the following (maps related) files:
