it would be a good idea to add some type of max upgrade button or a way to max an upgrade with like a shift click, the rebirth process and upgrading ack to where you where is just a lot or clicking upgrades.
Done, it is in demo-0.8. Shift+click on an upgrade takes as many levels as your stores allow, up to its cap, and the tooltip tells you how many before you click.
I counted before building it, because I wanted to know if it was comfort or a real problem: 454 purchase clicks in the first hour and 719 by the sixth run, with about seven clicks out of eight landing on a branch already chosen. So you were right.
I did not add a "buy everything" button: picking which branch to raise is the only real decision in the game, and one button would remove it. If rebuilding after a rebirth still feels long even with shift+click, say so and I will look at that on its own.