Hey Maurice, thanks for understanding! :) Regarding the two points:
In the case of point 1, if you do not delete your imported engines and just try importing again, SSS should keep your engine's order. At least it's doing that for me. :) It should only create a new engine if it doesn't find one with the same search URL already, and it shouldn't touch your ordering. If you are able to tell me how to reproduce this problem I would be grateful.
As for point 2, what are you using as the "Popup location" option under "Popup Behaviour"? The option to place the popup at the bottom left corner of the selection can behave strangely on some websites, because some pages' footer can cause you to select more than what is visible. If you are using "At cursor location" it should always appear above your cursor (but clamped to the top of the page). That said, this might be some SSS problem as well. :)
[previous reply 2018-02-12]
Hi! SSS actually did this before Firefox 57. :) Unfortunately, now it can't!
There's currently no way for WebExtension addons to look at your search engines, that's why I had to work around that problem by requesting the file from the user. These links on bugzilla discuss this problem, but nothing was completed yet:
Sorry, but this is something I can't do currently. :(
By the way, re-importing the json file should not reset existing engines but simply add those that are not there yet. If it is resetting existing engines then it could be a bug. Could you tell me what is happening exactly?
If you add new engines to Firefox frequently and have to re-import the json file, consider leaving in SSS all imported engines, but disable those you don't use instead of removing them. :)