[googie]

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

[googie]

...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/