Is there any tool for drawing circuit schematics (by "mouse clicking") which exports to TikZ?
There is no short answer to your question. To begin with,
TikZ is a part of the
(La)TeX ecosystem. That being said, it's a WYMIWYG (What You Mean Is What You Get) not WYSIWYG (What You See Is What You Get) kind of thing, so basically the very spirit in which it was created goes against 'drag-and-drop' kind of philosophy.
If you are using a library specifically designed for drawing circuits (e.g.
circuitikz or the
circuit library provided by
TikZ itself), I think you've run out of luck.
If, on the contrary, you have no problem drawing the shapes and then want to manipulate them, you can use
Inkscape and export to
TikZ with a plug-in. I have used it, you get working, albeit suboptimal
TikZ code, to say the least.
On a more personal note, I believe you should learn
TikZ. Once you master it, you will not need the rather complicated approach with
Inkscape and will have very readable code. You can try TeX.StackExcahge if stuck - the community is very friendly and responsive. I know it first hand, because I'm part of it.