I’ve been working through the examples and re-building them in CodeSandbox (I find it helpful to type out the code).
I seem to have found a bug in the underlines Decoration example. Using this minimal example: CM6 - underlines decoration example (broken?) - CodeSandbox, try highlighting some text and hitting Mod-H. It should underline the text immediately, however it does not appear until triggering the key bind a second time.
As far as I can tell, this CSB is identical to the code on the example page, however the example seems to work correctly. Am I missing something?
EDIT: forgot to add, I iterated on the example further based on my understanding of extensions and came up with this: CM6 - underlines decoration example (fixed/reconfigured) - CodeSandbox, which appears to work correctly.