At this moment navmesh generation tool is somewhat unintuitive and requires to do a lot of mundane actions and very prone to human errors.
Here's some QoL features that would made life a lot easier:

1. Add some kind of topdown view or map where you can just pick tiles to regenerate navmesh patch for. Current "Generator area" modal window approach with the South-West/"bottom-left" and North-East/"top-right" position usage is unintuitive and leads to a lof of excessive tiles to be captured increasing total mod size. Modders don't have a luxury of shipping full navmesh with the game itself as it would radically increase the mod size, which is pretty critical, especially on consoles.
2. Generator Area modal window could remember the last used position, as it's happens very often that you have to generate two navmesh patches (BTRLike and Soldiers) for the same coordinates.
3. Save navmesh Windows window (the one that appears after pressing OK on "Choose Navmesh" modal window) could remember the last used folder in "Other" subroute. At this moment it always defaults to ArmaReforger/data folder.