I use IntelliJ IDEA and often rely on their own Git functionality. But it cannot stage specific lines, only whole chunks [1]. For that, I've been using lazygit for a couple of months now. I like its simple UI and that it makes staging specific lines very easy and quick. If you like lazygit, you might also be interested in similar Git CLI clients that I collected here [2].
[1] https://youtrack.jetbrains.com/issue/IDEA-186988/Allow-commi...
[2] https://github.com/frontaid/git-cli-tools#clients