Hi,
Sorry if this is not the right place; please direct me if it isn’t.
I run up against this when I’m building a device and have to edit and recompile a lot. There is now an install button inside the edit window. But you need to validate before installing, which currently requires closing the edit window and then going into the menu on the side.
… but if the validate button was right there where you were coding …
Anyhoo. Just a convenience thing.
Feature requests for esphome typically go here 
But doesn’t the editor within the esphome dashboard actually does validation while typing and indicating wrong syntax and stuff directly? 
Uh … yes. Now I feel dumb.
Wait, no, here’s the use case.
Yes, the editor does underline code that is wrong, but unlike Validate, it doesn’t say why. Now, I just wasted half an hour looking for spacing errors because of an underlined block of code. It was not until I Validated it that I was told the reason why it was wrong, which in my case was because the config options of Neopixelbus had changed between versions.
So a Validate option from within the editor is still desirable because there may otherwise be no obvious reason that an error in the code exists.