Ha! I was going to reach out to you through a different channel, but here you are, on HN. :)
The import function is really slow.
I was recently playing with my pet project which is building an sqlite database from IMDB public datasets. It's 6Gb of CSV files into a ~12Gb database after a vacuum. With nodejs I can import the data within 6 minutes and create indexes and vacuum in another 4, which gives me a fully indexed database in just 10 minutes. With SQLStudio the import alone takes at least half an hour.
Probably not a typical use case for a sqlite database, but nevertheless, a decent benchmark.
BTW. Dobra robota! Dzięki! :)
In few days there will be another 3.4.x branch release (3.4.7), which addresses this exact problem - https://github.com/pawelsalawa/sqlitestudio/issues/5119
...or if you didn't mean the import() SQL function, but in general importing functionality (through Import Dialog) and it's still slow there, then please contact me and I will see what can be done to improve it - https://sqlitestudio.pl/contact/