TL;DR
Storing blueprints by Factorio version removes the need to clear the blueprints folder when switching between Factorio versionsWhat ?
Within the blueprints folder could be multiple sub-folders, each dedicated to storing blueprints for a specific version of Factorio.Bonus points would be awarded for following something along the lines of https://semver.org/ versioning to make blueprints accessible between compatible versions. If the main Factorio versioning system is not compliant an internal version that is compliant could be created to be used for this purpose.