Almost, a year ago, I did a quick hack to support wm_name.
As you said, it is very useful. For me, especially with some terminals in web browser like butterfly.

Here is the patch:
yoshinari-nomura@2a74e00

Concatenate window name into WM_CLASS

If you visit https://github.com/mooz/xkeysnail on Google
Chrome, xkeysnail will report WM_CLASS as follows:
WM_CLASS 'Google-chrome' | active keymaps = ...

After applying this patch, it will be:
WM_CLASS 'Google-chrome' (mooz/xkeysnail: Yet another
keyboard remapping tool for X environment - Google
Chrome)' | active keymaps = ...

This means we can change the keymaps according to the
window title. This is especially useful when you want to
change the keymap for each tab of the browser.

This patch, however, forces changes to the user's config.py

If possible, I wanted to add the window title as the second
parameter of the lambda function given to "define_keymap",
but the current xkeysnail doesn't support it.

It looks like there's a change that adds a device name to
the second parameter, but It doesn't seem to be working
well.

@yoshinari-nomura, @rbreaves Give #129 a try and see if it works for you.

@Lenbok This is awesome, I'll try and test it soon. I need to revise my fork a bit with the latest changes already. I think there are some old issues out there where I need to work on back porting some of my changes again but break it out into a different function so that it doesn't trip up some users existing keybinds. I need held key modifiers to be a thing on modifiers versus simply triggering a combo and immediately releasing the modifier even when it it is held, hence I need to create a KH() function and not just the default K(). That or add a paramter to K that would allow for held modifiers.

@Lenbok Great!
I have tried your hack. It works for me perfectly. Thank you!

By the way, why don't you show the device_name as well?
something like in transform.py:

print("WM_CLASS '{}' WM_NAME '{}' DEVICE_NAME '{}' | active keymaps = [{}]".format(wm_class, wm_name, device_name, ", ".join(keymap_names)))

@Lenbok Thank you again!

I've opened an issue against my fork to support WM_NAME in the context object passed to all conditionals. joshgoebel/keyszer#2 I've already done the backend work of making the whole conditional system more flexible (so we aren't just adding "yet another param" to a lambda). Adding this support (to keymap, modmap, and multi-modmap) should be trivial now. If anyone is comfortable running beta software and would like to contribute, get in touch! I still have a lot of balls in the air but things should hopefully be pretty stable in the next few days.