https://www.construct.net/en/make-games/manuals/construct-3/plugin-reference/local-storage
> Local Storage works offline, since it stores data to the device itself. Different browsers use different storages, so data is not shared between different browsers on the same computer - each browser has its own unique storage. This is also separate to the browser cache, which is temporary storage to avoid needlessly re-downloading the same files over and over again. However the user can usually still choose to clear local storage data from their browser (with an option perhaps named something like "clear offline website data"). Non-browser export options like NW.js, Cordova or Windows Store apps are not affected by the user clearing any amount of data from any browser, they also use separate storage. Finally for security reasons browsers use separate storage per domain. For example all content on construct.net shares the same storage, but content on facebook.com uses a different storage and cannot access any data saved from construct.net.
As described in the manual, each browser has its own default directory for saving data, so it is not Construct that decides where to save the data, but rather the browser currently used by the player.
And how do you actually find out where the browser is saving data?