We realize that this is a feature that quite a few users want, and are currently contemplating the best possible scenarios, also taking into account current limitations of how Weava currently functions (see bullet point #2).
Keyboard shortcut: E.g. similar to how you can disable/enable the highlighter with Alt+S (Option+S for Mac) and pin the sidebar with Alt+P (Option+P) and open/close the Weava sidebar with Alt+Shift+S (Option+Shift+S) there could be a keyboard shortcut that saves the website/pdf you are on. And keep in mind that these shortcuts are customizable in your own personal Chrome extension settings.
Option on pop-up: An option to click "bookmark" (e.g., a star icon) on the highlighter pop-up. This will require you to select some text however for the pop-up to appear.
If you have specific ideas of how the read later functionality should work, please comment below.